The ebooks distributed on the Kindle Store are distributed under a license that Amazon has negotiated. The GNU FDL does not permit redistributing under a different license. If the person submitting the book could assert that he was the author, and held copyright to the content, that would be one thing. If it is community authored, and edited by this person (as was actually asserted), Amazon would be opening themselves to actual legal liability from all of the other authors.
It's insane to me how many people who assert that Free Licenses are useful in such situations. This is the same as attempting to put some GPLed software on the App Store. It can be done, but only if everyone agrees to offer Apple an alternate license.