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edit index GNU General Public License
The GNU General Public License is a Copyleft software license. It was written by a programmer, Richard Stallman in 1989 of the Free Software Foundation (FSF), for the distribution of programs released as part of the GNU Project. Though based on similar licenses used for early versions of Emacs, the GPL license subtly challenged the notion of Copyright, and enforced its use on all code derived from "GPL'ed" code. Since its introduction, it has become one of the most widely-used, and also the most controversial, of software licenses. It was intended to provide more freedom instead of less, however, many legal disputes have arisen from licensees asserting the GPL restricted freedom. Other licenses created by the GNU project include the GNU Lesser General Public License and the GNU Free Documentation License.

Basic License Terms

Below follows a colloquial summary of the terms of the GPL. The only legal description, however, is that of the actual text of the GPL.

The licensee accepting these terms is given permission to modify the work, as well as to copy and redistribute the work or any derivative version, either free of charge or for a fee. This latter point distinguishes the GPL from software licenses that prohibit commercial redistribution. Stallman has argued that free software should not place restrictions on commercial use, and the GPL explicitly states that GPL'ed works may be (re)sold.

If the licensee distributes copies of the work, she is required to offer the source code to each recipient, including any modifications she had made. This requirement is known as Copyleft. In practice, GPL'ed programs are often bundled with the source code, although the license does not require this. Sometimes, only the source code is distributed, and the recipients are expected to compile it themselves.

The licensee is only required to provide the source code to people who received a copy from her, or alternatively to accompany binaries with an written offer of the source code to any third party. This means, for example, that one may make private modified versions of GPLed software, provided that the modified software is not distributed to anyone else. This applies, for example, if the licensee makes private modifications to the work but does not distribute them; in that case, she is not required to release her modifications to anyone.

Disputes and Criticism

Copyrights and Lefts

The FSF holds the Copyright for the text of the GPL, but it does not necessarily hold the Copyright for a work released under the GPL. Unless an explicit Copyright assignment is made to the FSF, the author of the work holds Copyright for the work, and is responsible for enforcing any violations of the license (or not).

Unlike the works released under the GPL, the GPL itself is not freely modifiable, since it is a software license. While copying and distribution is allowed, changing the text of the GPL is not allowed. How this squares with the fundamental right of other Copyright holders is what leads to disagreements. Because the work is copyrighted, a licensee has no modification or redistribution rights (barring Fair Use), except under the terms of the Copyleft, however, the licensee also has the right to release her work under any license of her choice - thus, conflicts often arise from the use of GPL software. Eben Moglen, General Counsel of the Free Software Foundation wrote:

"The GPL...subtracts from copyright rather than adding to it." - Eben Moglen
Thus, the user is only required to accept the terms of the GPL if she wishes to exercise rights normally restricted by copyright law, such as redistribution. Conversely, if a person distributes copies of the work (in particular, modified versions) while keeping the source code secret or otherwise violating the GPL, she can be sued by the original author under Copyright Law. This is a clever legal twist, and is the reason the GPL has been described as a "Copyright Hack", and even a "Virus". It also ensures that unlimited redistribution rights are not granted, should any legal flaw (or "bug") be found in the Copyleft statement.

Derivatives and Links

One of the key disputes related to the GPL is whether or not non-GPL software can dynamically link to GPL libraries. The GPL is clear in requiring that all derivative works of GPL code must themselves be GPL'ed. However, it is not clear whether an executable that dynamically links to a GPL library should be considered a derivative work. The free/open-source software community is split on this issue, with the FSF asserting that such an executable is indeed a derivative work, while some other experts disagree. This is ultimately a question not of the GPL per se, but of how Copyright Law defines derivative works, and there have been no clear court decisions to resolve this conflict.

Meanwhile, however, a number of businesses have become based upon distributing a GPL'ed library and selling a separate license to companies wishing to link the library with proprietary codes, whether dynamically or not. Examples of such companies include MySQL AB and Trolltech (Qt). In August 2003 SCO stated that they believed the GPL to have no legal validity, and that they intended to take up lawsuits over sections of code supposedly copied from SCO-Unix into the Linux kernel.

"The viral nature of open-source licensing nearly always applies to the General Public License. This is in part due to the terms of the GPL and also partly due to the position statements made by the authors of the GPL." - Phil Albert

GPL Programs

Since the GPL was written, a great number of programs have been released under it, which includes those forced to be released under it (due to Clause 2b of the GPL). Most of the programs in the GNU Project are licensed under either the GPL or the LGPL, including GCC, GNU Emacs, and the GNOME Desktop. Prominent programs which are not part of the GNU project, but are licensed under the GPL, include the following (Note: some of these were originally released under other licenses, and were only later made available under the GPL):



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Some content adapted from the Wikinfo article "GNU General Public License" under the GNU Free Documentation License.
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