Larry Sanger wrote:
Since I've posted the original text (which has since been modified) on Wikipedia, I no longer own the rights to the text. It is now released under the GNU FDL.
As a technical point, it is very much possible to both "own the rights" *and* release something under the GNU FDL.
Many authors of software, for example, donate their copyright to the Free Software Foundation. The GNU license is (presumably) as legally enforceable as Microsoft's license.
To license something, under more or less restrictive terms, is not the same as to give up ownership.