The basic idea of Creative Commons, offering free copyright tools, is copied from the free software movement. However, CC licenses are not intended to be used to release software, as our FAQ has always said.
One important reason why Creative Commons licenses should not be used to release software is that they aren’t compatible with existing free software licenses, most importantly the GPL from the Free Software Foundation, which is used by over half of free software projects. A commons fractured by legal incompatibilities is a weak commons, and it would be deeply contrary to our mission to fracture the commons of software. (It should also be noted that the FSF helped unfracture the non-software commons by facilitating Wikimedia’s migration to CC BY-SA as the main content license of Wikipedia and its sibling sites.)
While the vast majority of contemporary free software is released under the GPL or another free software license, there is also a long tradition of public domain software, which was free before the term free software existed. Indeed, prior to the 1970s, copyright did not apply to software. Currently, SQLite, an embedded database that you almost certainly use, is probably the most popular software that is dedicated to the public domain.
There are a variety of public domain dedications used to release software, which is mostly not a problem — to the extent such dedications are well-crafted, they don’t present a legal interoperability problem. This means it is possible to improve the state of the art in public domain dedications without harming the ecosystem. (Though this doesn’t mean an infinite variety of public domain dedications is optimal — at the extreme having to determine whether a new dedication is well-crafted each time one encounters a new public domain work would make using public domain works unattractive.)
In addition to licenses, Creative Commons also offers public domain tools. In creating the CC0 public domain dedication, we did set out to improve the state of the art in public domain dedications, and we think we’ve been pretty successful. Users seem to think so — ranging from governments and institutions to musicians.
We hadn’t set out with CC0 to improve on public domain dedications for software. However, since the release of CC0, we’ve been approached a number of times about using CC0 to dedicate software to the public domain. While we were happy to hear of this unanticipated demand, we wanted to tread very carefully so as to not create any unintended consequences for the free software ecosystem. This led to discussions with the Free Software Foundation, the steward of the GPL and moral leader of the free software movement.
We’re really happy to announce that the Free Software Foundation has added CC0 to its free software licenses list (which includes public domain terms). As usual, the FSF’s language is extremely clear, so we simply quote two sections from their list:
CC0 is a public domain dedication from Creative Commons. A work released under CC0 is dedicated to the public domain to the fullest extent permitted by law. If that is not possible for any reason, CC0 also provides a simple permissive license as a fallback. Both public domain works and the simple license provided by CC0 are compatible with the GNU GPL.
If you want to release your work to the public domain, we recommend you use CC0.
If you want to release your work to the public domain, we encourage you to use formal tools to do so. We ask people who make small contributions to GNU to sign a disclaimer form; that’s one solution. If you’re working on a project that doesn’t have formal contribution policies like that, CC0 is a good tool that anyone can use. It formally dedicates your work to the public domain, and provides a fallback license for cases where that is not legally possible.
We’ve also added an entry to the CC0 FAQ about using CC0 to release software, which you ought read if you’d like to do that. If you’re only familiar with the way CC licenses and public domain tools are typically used on web pages and other media, be aware that with free software, the full license (or public domain terms) are usually included with the software. In order to make this easy to do, we’ve taken this opportunity to fulfill a longstanding request — plain text copies of the “legalcode” for CC0 and CC’s six main international licenses. See CC software engineer Chris Webber’s post for details.
Special thanks to Chris Webber and the FSF’s Brett Smith for their persistent work to make the CC0 software recommendation possible.