Hm...
I recently took part in a FLOSS Manuals Inkscape documentation booksprint. Since my Inkscape knowledge is nothing special, I wrote a guide to contributing to Wikimedia Commons, in theory the manual being for people who were already familiar with Inkscape but not Wikimedia. http://en.flossmanuals.net/wikimediacommons
FLOSS Manuals is by default GPL. I asked for this manual to be dual-licensed with the GFDL so that its contents could be copied to a Wikimedia wiki if desired.
I was thinking I should copy the whole thing to Wikibooks as a book, but I wouldn't want to do that if the content couldn't be fed back into FLOSS Manuals (which has a wiki-to-print process that actually works, *now*).
GFDL did not win the free license race. It seems to me if you cut off dual licensing you are cutting off a lot of potential partnerships.
Is it so bad if you just put a template on each page of the book stating its dual license? This is what http://mediawiki.org does, which has a namespace of help docs which are PD, and intended to be exported with every wiki. All the rest is GFDL which just stays at mediawiki.org. See http://www.mediawiki.org/wiki/Template:PD_Help_Page
cheers Brianna [[user:pfctdayelise]]