That's interesting. Which part of the Knol TOS
specifically, is it #8:
http://knol.google.com/k/-/-/si57lahl1w25/12#
which grants Google the right to "modify" and "create derivative
works based on" what you submit to them? Why is that incompatible,
is it because this grants Google the right to "create derivative
works" which take out the sharealike requirement, and you're not
allowed to do that?
Yes, it's section 8. It's not anything unique to GFDL, you can't
upload anything to Knol that you didn't write yourself (or you have
explicit permission of the author) since you can't grant Google a
license to something you don't hold the copyright for. It's worth
noting that uploading someone else's work wouldn't be a copyright
violation because of that, it would just be a violation of Google's
terms of service, and Google would be committing a copyright violation
if they tried to use the license you were meant to grant them but
weren't legally able to.
(Again, IANAL, YMMV, etc., etc.)