Together with the Free Software Foundation, Creative Commons has officially proposed the GNU General Public License version 3 as a candidate for compatibility with CC BY-SA version 4.0. The announcement was made on the CC license development mailing list on January 29th, kicking off what will be at least a month-long discussion period before a final compatibility determination is made.
This proposal is significant because it would bridge a gap between two of the most widely-used copyleft licenses for code and content. Currently, developers are sometimes reluctant to integrate BY-SA content into GPL projects because of uncertainty about how the two licenses work together. Eliminating obstacles to remix between licenses so similar in aim and spirit is precisely what the compatibility mechanism in BY-SA was designed to do.
However, there are differences between the two licenses that pose issues for the CC and FSF communities to consider before declaring compatibility. Over the next several weeks, we will be leading a public discussion about those topics, ensuring the final decision will be informed by community input. We encourage anyone interested to join the discussion by signing up here.
GPLv3 is the second candidate for ShareAlike compatibility considered by Creative Commons. The Free Art License version 1.3 was considered under CC’s established compatibility process and criteria and was declared compatible in October 2014.