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You are here: Home Bulletins 2015 spring Demystifying copyleft

Demystifying copyleft

by Donald Robertson Contributions Published on Jul 08, 2015 05:35 PM

By Chrissie Himes, Operations Assistant and Donald Robertson, Copyright and Licensing Associate

Copyright is the legal mechanism afforded to the authors of original creative works, such as books, music, and software. Under 17 U.S. Code § 106, the exclusive rights granted to the artists are: (1) the right to reproduce the copyrighted work; (2) the right to prepare derivative works based upon the work; (3) the right to distribute copies of the work to the public; (4) the right to perform the copyrighted work publicly; and (5) the right to display the copyrighted work publicly.

Copyleft is a tool that works within copyright law, easing the process of licensing creative works to be used, retooled, and/or shared. For instance, you may have a new piece of software that you would like the general public to be able to build upon and fix bugs within. But under U.S. copyright law you possess the exclusive right to prepare derivative works. If you don't provide your users with a license, they won't be able to do all the things that they should be able to do, like modify and share the work. So while many projects think that simply putting the source code up on a repository is good enough to share their work, unless they choose and apply a license, all their hard work will go to waste. So choosing a good copyleft license that most communicates your intent is of great importance. The GNU General Public License (GPLv3) is a strong copyleft license that ensures not only that users have all the rights they need to share and modify your work, but that every downstream user has those same rights. The GNU Affero General Public License (AGPLv3) is also a strong copyleft license like the GPL, but with an additional provision that ensures that users interacting with modified versions of the code via a network have the opportunity to receive the source code. Finally, the GNU Lesser General Public License (LGPLv3) is a weak copyleft license. It allows users to link to the work under their own terms, while still ensuring that downstream users receiving modified versions of the work itself still have their rights intact.

While this brief introduction gives a basic idea of how copyleft works, there is plenty more to learn. In addition to information provided by the FSF via our licensing portal1 there is now another great resource for learning about copyleft licensing: is a collaborative project run jointly by the FSF and the Software Freedom Conservancy2 that pools and shares information about copyleft. This information is being made into a book, Copyleft and the GNU General Public License: A Comprehensive Tutorial and Guide. It combines resources developed by several organizations into one comprehensive guide. Is a continual work in progress, but the FSF will from time to time endorse and publish particular versions of the document. For example, we used the guide as part of the foundation for our continuing legal education (CLE) seminar on GPL Enforcement and Legal Ethics last year, and plan to use it for future CLE events.

But is more than just a collaboration between the FSF and the Software Freedom Conservancy: it is a community effort. Its tutorial and guide consist of over 150 pages of useful information, but it takes quite a bit of work to maintain. We invite everyone to help update and revise the guide. You don't need to be a legal whiz kid to help out; one of the biggest tasks to take on is copy editing. Every pull request helps, so dive in!


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