Encyclopedia  |   World Factbook  |   World Flags  |   Reference Tables  |   List of Lists     
   Academic Disciplines  |   Historical Timeline  |   Themed Timelines  |   Biographies  |   How-Tos     
Sponsor by The Tattoo Collection
Main Page | See live article | Alphabetical index


Copyleft is an additional (and irrevocable) provision in a copyright license that otherwise already grants certain freedoms to the licensee (i.e. the owner (of a copy) of a work that is governed by such copyright license). The preconditional freedoms are, generally, the free unlimited use, modification and redistribution of copies of the original work. The distinctive condition to that license for being also "copyleft" is that any modifications to the work (derivative works), if redistributed, must carry the same permissions (i.e. license terms), and must be made available in a form which facilitates modification. For software, this facilitating form is considered to be a synonym to source code, pre-supposing that all necessary compilation software is also freely available.

In normal speech copyleft is also used as a pars pro toto to indicate license conditions that include all the preconditional freedoms mentioned above (often also including freedom regarding sale of media and/or of auxiliary materials, e.g. documentation, which may carry a different copyright license), together with the actual copyleft condition.

Note that copyleft generally needs to hinge to copyright law for implementing an enforcable system for derivative works to be also released with a copyleft license (so "copyleft" pre-supposes at least some framework of "copyright" law, contrary to the popular belief that copyleft wants "to do away" with copyright as a whole). Also generally copyleft implies that the names of all contributors to a work keep attached to that work. These contributors are - for reasons of protecting the copyleft mechanism by copyright law - the pro forma copyright holders.

So long as all of those wanting to modify the work accept the terms, one of the net effects aimed at by copyleft is to facilitate successive improvement by a wide range of contributors. Those who are unwilling or unable to accept the terms are prohibited from creating derivative works.

Table of contents
1 History - definitional issues
2 Copyleft, Public Domain and Open Source - "strong", "weak", "full" and "partial" copyleft
3 Is copyleft "viral"?
4 Copyleft applied outside the context of copyright licensing for software
5 Commercial exploitation of copylefted creations
6 Related Topics
7 External links

History - definitional issues

The concept of copyleft arose when Richard Stallman was working on a Lisp interpreter. Symbolics asked to use 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 create a software license that would prevent this behavior which he named software hoarding. The term "copyleft" according to some source came from a message contained in Tiny BASIC, a free distributed version of Basic written by Dr. Wang in the late 1970s. The program listing contained the phrases "All Wrongs reserved" and "CopyLeft." Richard Stallman himself says the word comes from Don Hopkins, who he calls a very imaginative fellow, who mailed him a letter in 1984 or 1985 on which was written: "Copyleft—all rights reversed." [1]

There are definitional problems with the term "copyleft" which contribute to controversy over it. The term originated as an amusing backformation from the term "copyright", and was originally a noun, meaning the copyright license terms of the GNU General Public License (GPL) originated by Richard Stallman as part of the Free Software Foundation's work. Thus, "your program is covered by the copyleft" is almost considered as a synonym of the program being GPL-ed (GPL being the de facto standard of all kind of copyleft licenses). When used as a verb, as in "he copylefted his most recent version", it is less precise and can refer to any of several similar licenses, or indeed a notional imaginary license for discussion purposes. See also "strong" and "weak" copyleft discussion in next section.

Because of complications caused by use of software library routines, the FSF created the GNU Library General Public License (LGPL), which changes the requirement of further distribution in ways that make it possible to use a software library without being "infected" by its license. The LGPL was subsequently renamed to the GNU Lesser General Public License, in order to emphasize its implications and encourage software library authors to choose the ordinary GPL instead (also because LGPL is fundamentally not a copyleft license). [1]

Copyleft, Public Domain and Open Source - "strong", "weak", "full" and "partial" copyleft

No restrictions apply to works in the public domain. They may be freely modified, and the creator of the derivative work may license any new portions of the derivative work, but not the public domain portion, under any terms, or none. The resulting derivative work may not be available to the creators of the original or may compete with them. So, a public domain work is by definition not subject to full copyleft.

Copyleft is one of the key features distinguishing several types of open source software licenses (eventually copyleft became the key issue in the strife between the Open Source movement and the Free software movement): copyleft is the short name for a legal framework to ensure that derivatives of a licensed work stay free/open (which is not compulsory in a general "Open Source" approach). If the licensee of a copylefted work distributes derivative works not under the same (or in some cases: similar) copyleft license he will be facing legal consequences: for most copylefted works this implies at least that some provisions of the license are terminated, leaving the (former) licensee without permission to copy and/or distribute and/or publicly display and/or prepare derivative works of the software, etc.

Many open source software licenses, such as those used by the BSD operating systems, the X Window System and the Apache web server, are not copyleft licenses because they do not require the licensee to distribute derivative works under the same license. There is an ongoing debate as to which class of license provides a larger degree of freedom. This debate hinges on complex issues such as the definition of freedom and whose freedoms are more important. It is sometimes argued that the copyleft licenses attempt to maximize the freedom of all potential recipients in the future (freedom from the creation of proprietary software), while non-copyleft free software licenses maximize the freedom of the initial recipient (freedom to create proprietary software). It can also be seen as distinguishing the freedom of the individual software authors from the freedom of the software itself.

The copyleft governing a work is considered to be "stronger", to the degree that the copyleft provisions can be more efficiently enforced to all kinds of derived works. "Weak copyleft" is sometimes no more than an euphemism indicating that the work has no real enforcable copyleft.

An example of a free software license that uses strong copyleft is the GNU General Public License. Free software licenses that use "weak" copyleft include the GNU Lesser General Public License and the Mozilla Public License. Examples of non-copyleft free software licenses include the Q Public License, the X11 license, and the BSD licenses.

"Full" and "Partial" copyleft relate to another issue: Full copyleft is when all parts of a work (except the license itself!) can be modified by consecutive authors. Partial copyleft implies that some parts of the creation itself are made exempt of unlimited modification, or in another way not completely subject to all principles of copylefting. E.g. in artistic creation full copylefting is sometimes not possible or desirable (see below).

Is copyleft "viral"?

Copyleft licenses are sometimes referred to as viral copyright licenses, often by those who feel that they may lose out as a result, because any works derived from a copylefted work must themselves be copylefted. The term "viral" implies propagation like that of a biological virus through an entire organ of similar cells or species of similar bodies. In context of legally binding contracts and licenses, "viral" refers to anything, especially anything memetic, that propagates itself by attaching itself to something else, regardless of whether the viral assertions themselves add value to the individual work. The viral metaphor is over-used but is reasonable to help distinguish between free software and open source in software and documentation projects. Most advocates of copyleft argue that the analogy between copyleft and computer viruses does not apply. As they point out, computer viruses generally infect computers without the awareness of the user, whereas the copyleft actually grants the user certain permissions to distribute modified programs, which is not allowed under copyright law without permission of the copyright holder. Most proprietary software licenses do not allow such distribution. Furthermore, copyright itself is "viral" in this sense, since any works derived from a copyrighted work must have permission from and obey any conditions set by the original copyright holder.

The view that copyleft licenses are viral is supported by Microsoft, who say that if a product uses GPLed code, that product automatically escapes the creator's control and becomes GPLed, leaving the creator no recourse. Obviously, working for a software company will have a like effect. Advocates, including Eben Moglen, Professor of Law at Columbia University and counsel for the Free Software Foundation, note that this is not true since the GPL is a license, not a contract.

Microsoft, and others, in describing the GPL as a "viral license", may also be referring to the idea that any release of something new under the GPL would seem to create a positive feedback network effect, in which over time there will be an ever-expanding amount of copylefted code. Code reuse is often useful in software engineering, as a way to save effort and get on with a project, especially when a perfectly sensible design and implementation has already been done and is available. In contrast, those working on non-copylefted programs will have to "reinvent the wheel" for parts of their programs. This is often cited as a disadvantage of non-copylefted software development.

Many feel that copyleft licenses are desirable and popular for shared works precisely because they are viral, and apply to all derivative works, which are thus "infected" by the requirement to re-integrate changes deemed desirable by any party down the line. This requirement is seen as important because it ensures uniform license terms and free access, and makes copyleft projects resistant to unnecessary forking because all maintainers, of the original work or other versions, may use any modifications released by anyone. Useful changes tend to be merged, and different versions are maintained only to the extent that they are useful. Without the "viral" license, variant terms can apply to the forks, derivative works can be controlled commercially by the parties that extend or translate them, and the project would degrade to a mere "open source" one. It is thought that Linux has not suffered the same fragmentation as Unix because it is copylefted.

Copyleft applied outside the context of copyright licensing for software

Copyleft also inspired the arts (especially where traditional notions of intellectual property are experienced as hampering creativity and/or creative collaboration and/or easy distribution of art creations), with movements like the Libre Society and open-source record labels emerging. E.g. also the Free Art license is a copyleft license that can be applied to any work of art.

Copyleft licenses for materials other than software include the Creative Commons ShareAlike licenses and the GNU Free Documentation License (abbreviated to GNU FDL or GFDL or FDL). GFDL can be used to apply copyleft to works that have no distinghuishable source code (while the GPL definition relies on source code being distinghuisable from compiled code or object code or executable code or binary code in a work). GFDL is being used for the content of Wikipedia.

Note that the notion of copyleft, to make sense, somehow requires a space where hassle-free & cheap copying is common (...computer files or Xerox copies, etc): e.g. copyleft is more difficult to put in practice for those arts that are characterised by the production of unique objects, that can not be copied just like that - unless there is no fear of the unique original getting damaged. To illustrate this with an example: suppose there is a public display of some worldfamous paintings, and suppose an accidental visitor decides to "enhance" the paintings with some grattage and peinture brulée effects (not neglecting to sign his respectful contributions with some spray paint), then there is no (legal) way of stopping this guy if he can be considered copyleft licensee of these paintings. This - and other examples - may indicate that copyleft is not the ultimate philosopher's stone that would be able to solve all intellectual property related issues once and for all.

Copyleft licenses for art generally are aware of such limitations, so they differ from copyleft licenses for software, e.g. by making a distinction between the initial work and the copies (where some essential copyleft provisions are only applicable to the copies) and/or by leaning on notions that are less objective to put in practice (more like declarations of intent), for example stipulating copyleft to be subject to respect - in a programmers' world the implementation of copyleft itself is the maximum respect one can get. In other words: in art copyleft has to hinge on broader notions regarding authors' rights, which are even more complex (and more differing between countries) than mere copyright law.

Similarly, GFDL allows authors to use limiting techniques regarding their initial work, exempting some parts of their creation from the full copyleft mechanism, e.g. introducing "invariant sections", etc...

Copyleft-like ideas are also increasingly being suggested for patents (so, hinging on a patent law framework instead of on a copyright law framework), such as open patent pools that allow royalty-free use of patents contributed to the pool under certain conditions (such as surrendering the right to apply for new patents that are not contributed to the pool).

Commercial exploitation of copylefted creations

Whether art or industrial realisation, the commercial exploitation of rigourously copylefted creations has rules that are quite different from a traditional commercial exploitation via IPR. Several research projects (amongst which some by the EU, e.g. the FLOSS project), show that in order to make bussiness with Open Source Software either the copyleft aspect gets somehow overruled (e.g. by making money of temporary know-how advantages), either the business is developed exclusively on a model of services and/or consultancy surrounding the actual copylefted creations. Generally turnover (when expressed in financial terms) is expected to be much lower in a "copyleft" business than in a business that tries to exploit the sale of IPR. E.g. John Cage, and his heirs, would never have been able to make much money with the sale of printed music and public performance rights of the 4′ 33″ composition (which, from a commercial viewpoint, is, to put it exactly, hot air served at room temperature), plus throwing in an occasional lucrative litigation, weren't it for traditional exploitation of IPR. However, the impact on society of copylefted creations, can be much larger than the amount of sales of individual copylefted creations by it's creators lets expect, think e.g. Linux.

In art the concept of a "commercial service surrounding a copylefted creation" is maybe (even) harder to put in practice than in software development. Public performances could be considered as one of a few possibilities of providing such "services". Apart from the fact that not every artist is a born performer, an artist generally expects at least some kind of respect for his/her work (which is somehow undermined if applying the copyleft condition undiluted, i.e. without applying the additional conditions regarded as self-evident in a "conventional" artistic context, e.g. not mingling your own whistling to the sounds produced by a chamber ensemble in a concert - while rigourously copylefting a work without imposing additional conditions implicates renouncing to the right to see any deformation of that work as disrespectful, as long as it is known who operates the alterations). The conditions an artist has to live up to under strict copyleft licensing have something ruthlessly and self-denyingly adventurous, comparable to what Wikipedia has in bold on every "edit" page: "If you do not want your writing to be edited mercilessly and redistributed at will, do not submit it."

Often copylefted artistic creations can be seen to have a (supporting) publicity function, promoting other, more traditionally copyrighted creations by the same artist(s). Artists sticking to an uncompromising copylefting of the whole of their artistic output, could, in addition to services and consultancy, revert to some sort of patronage (generally considered as somehow limiting artistic freedom, even when state-operated like in some countries of northern Europe), or to other sources of income, not related to their artistic production (and so mostly limiting the time they can devote to artistic creation too). The least that can be said is that copylefting in art tends toward keeping the art thus produced as much as possible out of the commercial arena - which is considered as an intrinsic positive goal by some.

Related Topics

External links