CC-BY-NC-SA is an abbreviation of Creative Commons, by-attribution, non-commercial, share-alike. It refers to a Creative Commons License that allows reuse of content as long as attribution is given, the work is not reused commercially, and the content is maintained under the same license.
The license is not compatible with the GFDL, which is all Wikia are licensed under.
As of June 2005, all sister projects of Wikia are licensed under the CC-BY-NC-SA.
Désencyclopédie is the only Wikia that is allowed to contain content which is singly-licensed under the CC-BY-NC-SA (though of course wikis may multi-license their content under the GFDL and this license). See Désencyclopédie and Désencyclopédie:Project:Copyrights for full details of this.