Gerard Meijssen wrote:
... If this is correct, the consequence would be
that material that is not available under the GFDL should not be
included in a WMF project. ...
No. Assuming that "a WMF project" = any Wikimedia Foundation project, there
are ways to insert non-GFDL content into such projects, and not only
non-GFDL images (like CC-BY-SA) at Commons, en.Wikibooks, or elsewhere.
Read
http://en.wikisource.org/wiki/Wikisource:Copyright
"If you contribute source materials written by someone else to Wikisource
you thereby warrant that the source material is either public domain in the
United States or that you have permission from the copyright holder to
place the work on Wikisource."
I possibly misunderstood it, by I think that if I have some noncommercial or
no-derivates license (such as CC-BY-NC-ND), then I am allowed to upload
that source text to en.Wikisource.
-- [[Wikibooks:en:User:Kernigh]]