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copyleft: /kop'ee-left/ [play on `copyright'] n. 1. The copyright notice (`General Public License') carried by GNU EMACS and other Free Software Foundation software, granting reuse and reproduction rights to all comers (but see also General Public Virus). 2. By extension, any copyright notice intended to achieve similar aims.
The idea of copyleft originated with über-hacker Richard Stallman in 1983 when he started the GNU Project. In brief, his goal was "to develop a complete free Unix-like operating system." As part of that goal, he invented and wrote the GNU General Public License, a legal construct that included a copyright notice but added to it (or, technically, removed certain restrictions), so its terms allowed for the freedoms of reuse, modification and reproduction of a work or its derivatives to be kept for all.
Normal copyright asserts ownership and identification of the author, as well as prevents the use of the author's name as author of a distorted version of the work; it also prevents intentional distortion of the work by others and prevents destruction of the work. But it also carries other restrictions -- such as restricting the reproduction or modification of a work.
Copyleft contains the normal copyright statement, asserting ownership and identification of the author. However, it then gives away some of the other rights implicit in the normal copyright: it says that not only are you free to redistribute this work, but you are also free to change the work. However, you cannot claim to have written the original work, nor can you claim that these changes were created by someone else. Finally, all derivative works must also be placed under these terms.
Certain restrictions of copyright -- such as distribution and modification -- are not very useful to ``cyberia,'' the free, apolitical, democratic community that constitutes the internetworked digital world.
With computers, perfect copies of a digital work can easily be made -- and even modified, or further distributed -- by others, with no loss of the original work. As individuals interact in cyberia, sharing information -- then reacting and building upon it -- is not only natural, but this is the only way for individual beings to thrive in a community. In essence, the idea of copyleft is basic to the natural propagation of digital information among humans in a society. This is why the regular notion of copyright does not make sense in the context of cyberia.
Simple `public domain' publication will not work, because some will try to abuse this for profit by depriving others of freedom; as long as we live in a world with a legal system where legal abstractions such as copyright are necessary, as responsible artists or scientists we will need the formal legal abstractions of copyleft that ensure our freedom and the freedom of others.
Much literature has been written on this subject by Stallman, and the details can be found in the excellent texts published by the Free Software Foundation.
It is good enough! The GNU GPL is not only a document of significant historical and literary value, but it is in wide use today for countless software programs -- those as formal part of the GNU Project and otherwise. The GNU GPL originated for the specific goal of sharing software among computer programmers. However, looking closely at the GPL, it appears that the same License can be easily applied to non-software information.
Alternately, a document can be copylefted under different, or much simpler terms; whether or not the GNU GPL is the specific means to the end is not the issue, although the GNU GPL certainly provides the most explicit (and canonical) definition of copyleft.
It's simple. While a particular situation may require or inspire its own specific License, possibly similar to the GNU GPL, all that a copyleft notice must really do is fulfill the points as defined above in "First, what is Copyleft?". Using the GNU GPL to copyleft your work is easy.
The GNU GPL states that it "applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License," so this "Program," then, may not necessarily be a computer software program -- any work of any nature that can be copyrighted can be copylefted with the GNU GPL.
The GNU GPL references the "source code" of a work; this "source code" will mean different things for different kinds of information, but the definition of "source code" -- provided in the GNU GPL -- holds true in any case: "The source code for a work means the preferred form of the work for making modifications to it."
The notices attached to the work can not always be attached "to the start of each source file," as recommended by the GNU GPL. In this case, the directory that the files reside should contain a notice, as should any accompanying documentation or literature.
Finally, for non-software works the "copyright" line included at the start of the "source code" of the work is modified in language slightly:
<one line to give the work's name and a brief idea of what it does.> Copyright (C) 19yy <name of author> This information is free; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This work is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this work; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
Here are sources for further information on copyleft, especially as it is applied to non-software information:
The rest of this web site is the home of the GNU Project and is the canonical source for copyleft and freely-redistributable software.
Ram Samudrala wrote the Free Music Philosophy and creates copylefted music as the band Twisted Helices.
Some of my own non-software copylefted works include texts ( literature, reviews, and technical) and music.
Copyright 1997 Michael Stutz
Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved.
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Updated: 5 Oct 2000 taz