Alex-
If they are agreeing to release their material under
the GFDL
they have the right to be cited as at least one of the five
most major contributors to the article. it says this in the
GFDL.
They are agreing to release it into the public domain, so that's not an
issue.
While I'm talking to a lawyer -- a completely unreleated issue: Do you
know whether the text of patent documents (i.e. the description of patent
claims filed with the USPTO) is copyrighted or not? The USPTO offers these
documents for free download, but I'm not sure if it would be legal for us
to use extensive quotes (beyond fair use) from recently filed patents. I
did a Google search but that's really difficult with only "patent"
"copyright" and "public domain" as possible search words, as you can
imagine ..
Regards,
Erik