Don Hopkins is an artist and programmer specializing in human computer interaction and computer graphics . He is an alumnus of the University of Maryland and a former member of the University of Maryland Human–Computer Interaction Lab .
79-824: Higher categories: Software , freedom Copyleft is the legal technique of granting certain freedoms over copies of copyrighted works with the requirement that the same rights be preserved in derivative works . In this sense, freedoms refers to the use of the work for any purpose, and the ability to modify, copy, share, and redistribute the work, with or without a fee. Licenses which implement copyleft can be used to maintain copyright conditions for works ranging from computer software , to documents , art , and scientific discoveries, and similar approaches have even been applied to certain patents . Copyleft software licenses are considered protective or reciprocal in contrast with permissive free software licenses , and require that information necessary for reproducing and modifying
158-509: A vulnerability . Software patches are often released to fix identified vulnerabilities, but those that remain unknown ( zero days ) as well as those that have not been patched are still liable for exploitation. Vulnerabilities vary in their ability to be exploited by malicious actors, and the actual risk is dependent on the nature of the vulnerability as well as the value of the surrounding system. Although some vulnerabilities can only be used for denial of service attacks that compromise
237-520: A web application —had become the primary method that companies deliver applications. Software companies aim to deliver a high-quality product on time and under budget. A challenge is that software development effort estimation is often inaccurate. Software development begins by conceiving the project, evaluating its feasibility, analyzing the business requirements, and making a software design . Most software projects speed up their development by reusing or incorporating existing software, either in
316-457: A change request. Frequently, software is released in an incomplete state when the development team runs out of time or funding. Despite testing and quality assurance , virtually all software contains bugs where the system does not work as intended. Post-release software maintenance is necessary to remediate these bugs when they are found and keep the software working as the environment changes over time. New features are often added after
395-486: A code's correct and efficient behavior, its reusability and portability , or the ease of modification. It is usually more cost-effective to build quality into the product from the beginning rather than try to add it later in the development process. Higher quality code will reduce lifetime cost to both suppliers and customers as it is more reliable and easier to maintain . Software failures in safety-critical systems can be very serious including death. By some estimates,
474-452: A copyleft-licensed work are expected to reciprocate the author's action of copyleft-licensing the software by also copyleft-licensing any derivatives they might have made. Because of this requirement, copyleft licenses have also been described as "viral" due to their self-perpetuating terms. In addition to restrictions on copying, copyleft licenses address other possible impediments. They ensure that rights cannot be later revoked , and require
553-556: A divisive issue in the ideological strife between the Open Source Initiative and the free software movement . However, there is evidence that copyleft is both accepted and proposed by both parties: " Viral license " is a pejorative name for copyleft licenses. It originates from the terms 'General Public Virus' or 'GNU Public Virus' (GPV), which dates back to 1990, a year after the GPLv1 was released. The name 'viral license' refers to
632-417: A fee. Unlike similar permissive licenses that also grant these freedoms, copyleft licenses also ensure that any modified versions of a work covered by a copyleft license must also grant these freedoms. Thus, copyleft licenses have conditions: that modifications of any work licensed under a copyleft license must be distributed under a compatible copyleft scheme and that the distributed modified work must include
711-496: A frequently cited paper about pie menus at CHI'88 with John Raymond Callahan, Ben Shneiderman and Mark Weiser . He has published many free software and open source implementations of pie menus for X10 , X11, NeWS , Tcl/tk , ScriptX , ActiveX , JavaScript , OpenLaszlo , Python and OLPC , and also proprietary implementations for The Sims and the Palm Pilot . Hopkins also wrote demonstrations and programming examples of
790-443: A legal regime where liability for software products is significantly curtailed compared to other products. Source code is protected by copyright law that vests the owner with the exclusive right to copy the code. The underlying ideas or algorithms are not protected by copyright law, but are often treated as a trade secret and concealed by such methods as non-disclosure agreements . Software copyright has been recognized since
869-570: A letter in 1984 or 1985, on which was written: "Copyleft – all rights reversed ", which is a pun on the common copyright disclaimer " all rights reserved ". In France , a series of meetings taking place in 2000 under the title "Copyleft Attitude" gave birth to the Free Art License (FAL), theoretically valid in any jurisdiction bound by the Berne Convention and recommended by Stallman's own Free Software Foundation . Shortly thereafter,
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#1733104582064948-576: A license that allows one to use GNU GPL in combination with a limited warranty. For projects which will be run over a network, a variation of the GNU GPL, called the Affero General Public License (GNU AGPL), ensures that the source code is available to users of software over a network. Copyleft is a distinguishing feature of some free software licenses, while other free-software licenses are not copyleft licenses because they do not require
1027-485: A means of modifying the work. Under fair use , however, copyleft licenses may be superseded, just like regular copyrights. Therefore, any person utilizing a source licensed under a copyleft license for works they invent is free to choose any other license (or none at all) provided they meet the fair use standard. Copyleft licenses necessarily make creative use of relevant rules and laws to enforce their provisions. For example, when using copyright law, those who contribute to
1106-419: A program's users, no matter what subsequent revisions anyone made to the original program. This original GPL did not grant rights to the public at large, only those who had already received the program; but it was the best that could be done under existing law. The new license was not at this time given the copyleft label. Richard Stallman stated that the use of "Copyleft" comes from Don Hopkins , who mailed him
1185-404: A quick web search . Most creative professionals have switched to software-based tools such as computer-aided design , 3D modeling , digital image editing , and computer animation . Almost every complex device is controlled by software. Don Hopkins He inspired Richard Stallman , who described him as a "very imaginative fellow", to use the term copyleft . He coined Deep Crack as
1264-520: A separate, unrelated initiative in the United States yielded the Creative Commons license , available since 2001 in several different versions (only some of which can be described as copyleft) and more specifically tailored to U.S. law. While copyright law gives software authors control over copying, distribution and modification of their works, the goal of copyleft is to give all users of the work
1343-495: A significant role in the distribution of software products. The first use of the word software is credited to mathematician John Wilder Tukey in 1958. The first programmable computers, which appeared at the end of the 1940s, were programmed in machine language . Machine language is difficult to debug and not portable across different computers. Initially, hardware resources were more expensive than human resources . As programs became complex, programmer productivity became
1422-509: A specific version of the software, downloaded, and run on hardware belonging to the purchaser. The rise of the Internet and cloud computing enabled a new model, software as a service (SaaS), in which the provider hosts the software (usually built on top of rented infrastructure or platforms ) and provides the use of the software to customers, often in exchange for a subscription fee . By 2023, SaaS products—which are usually delivered via
1501-415: A system's availability, others allow the attacker to inject and run their own code (called malware ), without the user being aware of it. To thwart cyberattacks, all software in the system must be designed to withstand and recover from external attack. Despite efforts to ensure security, a significant fraction of computers are infected with malware. Programming languages are the format in which software
1580-417: A work (except the license itself) may only be modified and distributed under the terms of the work's copyleft license. Partial copyleft, by contrast, exempts some parts of the work from the copyleft provisions, permitting distribution of some modifications under terms other than the copyleft license, or in some other way does not impose all the principles of copylefting on the work. An example of partial copyleft
1659-489: A work under copyleft usually must gain, defer, or assign copyright holder status. By submitting the copyright of their contributions under a copyleft license, they deliberately give up some of the rights that normally follow from copyright, including the right to be the unique distributor of copies of the work. Some laws used for copyleft licenses vary from one country to another, and may also be granted in terms that vary from country to country. For example, in some countries, it
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#17331045820641738-733: Is a mirrored version of the copyright symbol , © : a reversed C in a circle. A 2016 proposal to add the symbol to a future version of Unicode was accepted by the Unicode Technical Committee . The code point U+1F12F 🄯 COPYLEFT SYMBOL was added in Unicode 11 . The copyleft symbol has no legal status. As of 2024, the symbol is generally provided as standard in the system fonts of most current operating systems , but if need be it may be approximated with character U+2184 ↄ LATIN SMALL LETTER REVERSED C between parenthesis (ɔ) . On modern computer systems,
1817-537: Is acceptable to sell a software product without warranty, in standard GNU General Public License style, while in most European countries it is not permitted for a software distributor to waive all warranties regarding a sold product. For this reason, the extent of such warranties is specified in most European copyleft licenses, for example, the European Union Public Licence (EUPL), or the CeCILL license ,
1896-677: Is copyleft under the Creative Commons Attribution-ShareAlike license. Li-Chen Wang 's Palo Alto Tiny BASIC for the Intel 8080 appeared in Dr. Dobb's Journal in May 1976. The listing begins with the title, author's name, and date, but also has "@COPYLEFT ALL WRONGS RESERVED". The concept of copyleft was described in Richard Stallman 's GNU Manifesto in 1985, where he wrote: GNU
1975-401: Is determined by the extent to which its provisions can be imposed on all kinds of derivative works. Thus, the term "weak copyleft" refers to licenses where not all derivative works inherit the copyleft license; whether a derivative work inherits or not often depends on how it was derived. "Weak copyleft" licenses are often used to cover software libraries . This allows other software to link to
2054-427: Is more important than a copyleft. Common practice for using copyleft is to codify the copying terms for a work with a license . Any such license typically includes all the provisions and principles of copyleft inside the license's terms. This includes the freedom to use the work, study the work, copy, and share the work with others, modify the work, and distribute exact or modified versions of that work, with or without
2133-476: Is no reason to believe the GPL could force proprietary software to become free software, but could "try to enjoin the firm from distributing commercially a program that combined with the GPL'd code to form a derivative work, and to recover damages for infringement." If the firm "actually copied code from a GPL'd program, such a suit would be a perfectly ordinary assertion of copyright, which most private firms would defend if
2212-400: Is not in the public domain. Everyone will be permitted to modify and redistribute GNU, but no distributor will be allowed to restrict its further redistribution. That is to say, proprietary modifications will not be allowed. I want to make sure that all versions of GNU remain free. Stallman's motivation was that a few years earlier he had worked on a Lisp interpreter. Symbolics asked to use
2291-420: Is that derived works must also be released under a compatible copyleft license. This is due to the underlying principle of copyleft: that anyone can benefit freely from the previous work of others, but that any modifications to that work should benefit everyone else as well, and thus must be released under similar terms. For this reason, copyleft licenses are also known as reciprocal licenses: any modifiers of
2370-524: Is that not everyone wants to share their work, and some share-alike agreements require that the whole body of work be shared, even if the author only wants to share a certain part. The plus side for an author of source code is that any modification to the code will not only benefit the original author but that the author will be recognized and ensure the same or compatible license terms cover the changed code. Some Creative Commons licenses are examples of share-alike copyleft licenses. Those licenses grant users of
2449-496: Is the GPL linking exception made for some software packages. The " share-alike " condition in some licenses imposes the requirement that any freedom that is granted regarding the original work must be granted on exactly the same or compatible terms in any derived work. This implies that any copyleft license is automatically a share-alike license but not the other way around, as some share-alike licenses include further restrictions such as prohibiting commercial use. Another restriction
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2528-453: Is written. Since the 1950s, thousands of different programming languages have been invented; some have been in use for decades, while others have fallen into disuse. Some definitions classify machine code —the exact instructions directly implemented by the hardware—and assembly language —a more human-readable alternative to machine code whose statements can be translated one-to-one into machine code—as programming languages. Programs written in
2607-531: The GNU General Public License (GPL), originally written by Richard Stallman , which was the first software copyleft license to see extensive use; the Mozilla Public License ; the Free Art License ; and the Creative Commons share-alike license condition —with the last two being intended for non-software works, such as documents and pictures, both academic or artistic in nature. Misplaced Pages
2686-531: The GNU Lesser General Public License and the Mozilla Public License . The GNU General Public License is an example of a license implementing strong copyleft. An even stronger copyleft license is the AGPL , which requires the publishing of the source code for software as a service use cases. The Sybase Open Watcom Public License is one of the strongest copyleft licenses, as this license closes
2765-529: The OLPC XO-1 laptop . The current version includes pie menus and is explained in depth in a video released by Hopkins. Since its primary objective is education, the OLPC project is looking not just for games, but for tools that enable kids to program their own games. Hopkins programmed Micropolis to make it easy to extend in many interesting ways. He added functionality to let kids create new disasters and agents (like
2844-438: The high-level programming languages used to create software share a few main characteristics: knowledge of machine code is not necessary to write them, they can be ported to other computer systems, and they are more concise and human-readable than machine code. They must be both human-readable and capable of being translated into unambiguous instructions for computer hardware. The invention of high-level programming languages
2923-605: The machine language specific to the hardware. The introduction of high-level programming languages in 1958 allowed for more human-readable instructions, making software development easier and more portable across different computer architectures . Software in a programming language is run through a compiler or interpreter to execute on the architecture's hardware. Over time, software has become complex, owing to developments in networking , operating systems , and databases . Software can generally be categorized into two main types: The rise of cloud computing has introduced
3002-645: The FSF asserts it does not and explicitly adds an exception allowing it in the license for the GNU Classpath re-implementation of the Java library. This ambiguity is an important difference between the GPL and the LGPL , in that the LGPL specifically allows linking or compiling works licensed under terms that are not compatible with the LGPL, with works covered by the LGPL. The copyleft symbol
3081-462: The GPL poses a threat to the intellectual property of any organization making use of it." In another context, Steve Ballmer declared that code released under GPL is useless to the commercial sector, since it can only be used if the resulting surrounding code is licensed under a GPL-compatible license, and described it thus as "a cancer that attaches itself in an intellectual property sense to everything it touches". In response to Microsoft's attacks on
3160-430: The GPL, several prominent free-software developers and advocates released a joint statement supporting the license. According to FSF compliance engineer David Turner, the term "viral license" creates a misunderstanding and a fear of using copylefted free software. While a person can catch a virus without active action, license conditions take effect upon effective usage or adoption. David McGowan has also written that there
3239-481: The Lisp interpreter, and Stallman agreed to supply them with a public domain version of his work. Symbolics extended and improved the Lisp interpreter, but when Stallman wanted access to the improvements that Symbolics had made to his interpreter, Symbolics refused. Stallman then, in 1984, proceeded to work towards eradicating this emerging behavior and culture of proprietary software , which he named software hoarding . This
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3318-523: The ScriptX multimedia scripting language created by the Apple/IBM research spinoff Kaleida Labs , developed various OpenLaszlo applications and components, and is a hacker artist known for his artistic cellular automata. He is also known for having written a chapter "The X-Windows Disaster" on X Window System in the book The UNIX-HATERS Handbook . Hopkins, supported by John Gilmore , adapted SimCity for
3397-481: The availability of both types of licenses, copyleft and permissive, allow authors to choose the type under which to license the works they invent. For documents, art, and other works other than software and code, the Creative Commons share-alike licensing system and the GNU Free Documentation License (GFDL) allow authors to apply limitations to certain sections of their work, exempting some parts of
3476-399: The bottleneck. The introduction of high-level programming languages in 1958 hid the details of the hardware and expressed the underlying algorithms into the code . Early languages include Fortran , Lisp , and COBOL . There are two main types of software: Software can also be categorized by how it is deployed . Traditional applications are purchased with a perpetual license for
3555-439: The character U+1F12F 🄯 COPYLEFT SYMBOL can be generated using one of these methods ( keyboard shortcuts ): Software Software consists of computer programs that instruct the execution of a computer . Software also includes design documents and specifications. The history of software is closely tied to the development of digital computers in the mid-20th century. Early programs were written in
3634-453: The communication is abstract, such as executing a command-line tool with a set of switches or interacting with a web server. As a consequence, even if one module of an otherwise non-copyleft product is placed under the GPL, it may still be legal for other components to communicate with it in ways such as these. This allowed communication may or may not include reusing libraries or routines via dynamic linking – some commentators say it does,
3713-404: The correctness of code, while user acceptance testing helps to ensure that the product meets customer expectations. There are a variety of software development methodologies , which vary from completing all steps in order to concurrent and iterative models. Software development is driven by requirements taken from prospective users, as opposed to maintenance, which is driven by events such as
3792-400: The cost of poor quality software can be as high as 20 to 40 percent of sales. Despite developers' goal of delivering a product that works entirely as intended, virtually all software contains bugs. The rise of the Internet also greatly increased the need for computer security as it enabled malicious actors to conduct cyberattacks remotely. If a bug creates a security risk, it is called
3871-419: The cost of products. Unlike copyrights, patents generally only apply in the jurisdiction where they were issued. Engineer Capers Jones writes that "computers and software are making profound changes to every aspect of human life: education, work, warfare, entertainment, medicine, law, and everything else". It has become ubiquitous in everyday life in developed countries . In many cases, software augments
3950-447: The fact that any works derived from a copyleft work must preserve the copyleft permissions when distributed. Some advocates of the various BSD Licenses used the term derisively in regards to the GPL's tendency to absorb BSD-licensed code without allowing the original BSD work to benefit from it, while at the same time promoting itself as "freer" than other licenses. Microsoft vice-president Craig Mundie remarked, "This viral aspect of
4029-438: The form of commercial off-the-shelf (COTS) or open-source software . Software quality assurance is typically a combination of manual code review by other engineers and automated software testing . Due to time constraints, testing cannot cover all aspects of the software's intended functionality, so developers often focus on the most critical functionality. Formal methods are used in some safety-critical systems to prove
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#17331045820644108-403: The freedom and permission to reproduce, adapt , or distribute it, copyleft licenses are distinct from other types of copyright licenses that limit such freedoms. Instead of allowing a work to fall completely into the public domain , where no ownership of copyright is claimed, copyleft allows authors to impose restrictions on the use of their work. One of the main restrictions imposed by copyleft
4187-597: The freedom to carry out all of these activities. These freedoms (from the Free Software Definition ) include: Similar terms are present in the Open Source Definition , a separate definition that contains similar freedoms. The vast majority of copyleft licenses satisfy both definitions, that of the Free Software Definition and Open Source Definition. By guaranteeing viewers and users of a work
4266-439: The functionality of existing technologies such as household appliances and elevators . Software also spawned entirely new technologies such as the Internet , video games , mobile phones , and GPS . New methods of communication, including email , forums , blogs , microblogging , wikis , and social media , were enabled by the Internet. Massive amounts of knowledge exceeding any paper-based library are now available with
4345-557: The library and be redistributed without the requirement for the linking software to also be licensed under the same terms. Only changes to the software licensed under a "weak copyleft" license become subject itself to copyleft provisions of such a license. This allows programs of any license to be compiled and linked against copylefted libraries such as glibc and then redistributed without any re-licensing required. The concrete effect of strong vs. weak copyleft has yet to be tested in court. Free-software licenses that use "weak" copyleft include
4424-438: The licensee to distribute derivative works under the same license. There is an ongoing debate as to which class of license provides the greater degree of freedom. This debate hinges on complex issues, such as the definition of freedom and whose freedoms are more important: the potential future recipients of a work (freedom from proprietization) or just the initial recipient (freedom to proprietize). However, current copyright law and
4503-597: The mid-1970s and is vested in the company that makes the software, not the employees or contractors who wrote it. The use of most software is governed by an agreement ( software license ) between the copyright holder and the user. Proprietary software is usually sold under a restrictive license that limits copying and reuse (often enforced with tools such as digital rights management (DRM)). Open-source licenses , in contrast, allow free use and redistribution of software with few conditions. Most open-source licenses used for software require that modifications be released under
4582-522: The monster, tornado, helicopter and train), and program them like in many of the other games on the XO. The goals of deeply integrating SimCity with OLPC's Sugar user interface are to focus on education and accessibility for younger kids, as well as motivating and enabling older kids to learn programming. The Sims is a simulation video game developed by Electronic Arts . The games are known for their very loose guidelines and no specific user goals. They allow
4661-565: The name of the EFF DES cracker . He ported the SimCity computer game to several versions of Unix and developed a multi player version of SimCity for X11, did much of the core programming of The Sims , and developed robot control and personality simulation software for Will Wright 's Stupid Fun Club. He developed and refined pie menus for many platforms and applications including window managers , Emacs , SimCity and The Sims , and published
4740-627: The new software delivery model Software as a Service (SaaS). In SaaS, applications are hosted by a provider and accessed over the Internet . The process of developing software involves several stages. The stages include software design , programming , testing , release , and maintenance . Software quality assurance and security are critical aspects of software development, as bugs and security vulnerabilities can lead to system failures and security breaches. Additionally, legal issues such as software licenses and intellectual property rights play
4819-472: The operating system) can take this saved file and execute it as a process on the computer hardware. Some programming languages use an interpreter instead of a compiler. An interpreter converts the program into machine code at run time , which makes them 10 to 100 times slower than compiled programming languages. Software is often released with the knowledge that it is incomplete or contains bugs. Purchasers knowingly buy it in this state, which has led to
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#17331045820644898-604: The physical world may also be part of the requirements for a software patent to be held valid. Software patents have been historically controversial . Before the 1998 case State Street Bank & Trust Co. v. Signature Financial Group, Inc. , software patents were generally not recognized in the United States. In that case, the Supreme Court decided that business processes could be patented. Patent applications are complex and costly, and lawsuits involving patents can drive up
4977-425: The quality of their software to compete with free software. This may also have the effect of preventing monopolies in areas dominated by proprietary software. However, competition with proprietary software can also be a reason to forgo copyleft. The Free Software Foundation recommends that when "widespread use of the code is vital for advancing the cause of free software", allowing the code to be copied and used freely
5056-408: The release. Over time, the level of maintenance becomes increasingly restricted before being cut off entirely when the product is withdrawn from the market. As software ages , it becomes known as legacy software and can remain in use for decades, even if there is no one left who knows how to fix it. Over the lifetime of the product, software maintenance is estimated to comprise 75 percent or more of
5135-424: The same license, which can create complications when open-source software is reused in proprietary projects. Patents give an inventor an exclusive, time-limited license for a novel product or process. Ideas about what software could accomplish are not protected by law and concrete implementations are instead covered by copyright law . In some countries, a requirement for the claimed invention to have an effect on
5214-409: The shoe were on the other foot." Richard Stallman has described this view with an analogy, saying, "The GPL's domain does not spread by proximity or contact, only by deliberate inclusion of GPL-covered code in your program. It spreads like a spider plant , not like a virus." Popular copyleft licenses, such as the GPL, have a clause allowing components to interact with non-copyleft components as long as
5293-713: The so-called "private usage" loophole of the GPL, and requires the publishing of source code in any use case. For this reason, the license is considered non-free by the Free Software Foundation , the GNU Project , and the Debian project. However, the license is accepted as open source by the OSI . The Design Science License (DSL) is a strong copyleft license that applies to any work, not only software or documentation, but also literature, artworks, music, photography, and video. DSL
5372-487: The software the same freedoms as copyleft licenses but do not require modified versions of that software to also include those freedoms. They have minimal restrictions on how the software can be used, modified, and redistributed, and are thus not copyleft licenses. Examples of this type of license include the X11 license , Apache license , Expat license , and the various BSD licenses . It has been suggested that copyleft has become
5451-695: The software. Some creators, such as Elastic , feel that preventing commercial enterprises from using and then selling their product under a proprietary license is also an incentive. Furthermore, the open-source culture of programming has been described as a gift economy , where social power is determined by an individual's contributions. Contributing to or creating open-source, copyleft-licensed software of high quality can lead to contributors gaining valuable experience and can lead to future career opportunities. Copyleft software has economic effects beyond individual creators. The presence of quality copyleft software can force proprietary software developers to increase
5530-431: The total development cost. Completing a software project involves various forms of expertise, not just in software programmers but also testing, documentation writing, project management , graphic design , user experience , user support, marketing , and fundraising. Software quality is defined as meeting the stated requirements as well as customer expectations. Quality is an overarching term that can refer to
5609-467: The users to simply exist in the virtual world they create. Don Hopkins became involved in The Sims after he worked at Sun Microsystems . The Sims were a theme in his work since then and he has contributed to much of the design and conceptual development of the game. He was hired to port The Sims to Unix. He implemented the usage of pie menus to the game so that users could efficiently carry out actions in
5688-524: The work and its derivatives to be provided in a form that allows further modifications to be made. In software , this means requiring that the source code of the derived work be made available together with the software itself. The economic incentives to work on copyleft content can vary. Traditional copyright law is designed to promote progress by providing economic benefits to creators. When choosing to copyleft their work, content creators may seek complementary benefits like recognition from their peers. In
5767-449: The work from the full copyleft mechanism. In the case of the GFDL, these limitations include the use of invariant sections, which may not be altered by future editors. The initial intention of the GFDL was as a device for supporting the documentation of copylefted software. However, the result is that it can be used for any kind of document. The strength of the copyleft license governing a work
5846-464: The work must be made available to recipients of the software program, which are often distributed as executables . This information is most commonly in the form of source code files, which usually contain a copy of the license terms and acknowledge the authors of the code. Copyleft helps ensure everyone's rights to freely use the product but it prohibits owning, registering copyright and earning royalties from copyright. Notable copyleft licenses include
5925-494: The world of computer programming, copyleft-licensed computer programs are often created by programmers to fill a need they have noticed. Such programs are often published with a copyleft license simply to ensure that subsequent users can also freely use modified versions of that program. This is especially true for creators who wish to prevent "open source hijacking", or the act of reusing open-source code and then adding extra restrictions to it, an action prevented by copyleft-licensing
6004-526: The wrongs he perceived it to perpetuate, he decided to work within the framework of existing law; in 1985, he created his own copyright license, the Emacs General Public License, the first copyleft license. This later evolved into the GNU General Public License , which is now one of the most popular free-software licenses. For the first time, a copyright holder had taken steps to ensure that the maximal number of rights be perpetually transferred to
6083-434: Was not the first time Stallman had dealt with proprietary software, but he deemed this interaction a "turning point". He justified software sharing, protesting that when sharing, the software online can be copied without the loss of the original piece of work. The software can be used multiple times without ever being damaged or worn out. As Stallman deemed it impractical in the short term to eliminate current copyright law and
6162-401: Was simultaneous with the compilers needed to translate them automatically into machine code. Most programs do not contain all the resources needed to run them and rely on external libraries . Part of the compiler's function is to link these files in such a way that the program can be executed by the hardware. Once compiled, the program can be saved as an object file and the loader (part of
6241-474: Was written by Michael Stutz after he took an interest in applying GNU-style copyleft to non-software works, which later came to be called libre works . In the 1990s, it was used on music recordings, visual art, and even novels. It is not considered compatible with the GNU GPL by the Free Software Foundation. "Full" and "partial" copyleft relate to another issue. Full copyleft exists when all parts of
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