2009/4/14 Marcin Cieslak saper@system.pl:
"2. to require continued dual-licensing of new community edits in this manner, but allow content from third parties to be under CC-BY-SA only;"
My understanding of that clause has always been that if something is first published on a Wikimedia project then it has to be dual licensed, if it is published elsewhere first, then it can be CC only. (This does mean that anyone wanting to bypass the dual licensing can do so rather easily, but that's the FSF's problem - they are the ones that required the dual licensing.)