This is the biggest news item [1] for free culture and free software in the past 5 years: The creativecommons attribution sharealike license is now one-way compatible to the GPL — see the message from creativecommons [2] and from the Free Software Foundation [3].
Some license compatibility legalese might sound small, but the impact of this is hard to overestimate.
(I’ll now revise some of my texts about licensing — CC BY-SA got a major boost in utility because it not longer excludes usage in copyleft documents which need the source to have a defended sharealike clause)
Links:
[1] http://lists.ibiblio.org/pipermail/cc-licenses/2015-October/007699.html
[2] http://creativecommons.org/weblog/entry/46186
[3] http://www.fsf.org/blogs/licensing/creative-commons-by-sa-4-0-declared-one-way-compatible-with-gnu-gpl-version-3
[4] http://blender.org
[5] http://reprap.org/
[6] http://wikipedia.org
[7] http://ryzom.com/
[8] http://wesnoth.org
[9] http://1w6.org/english/flyerbook-rules