So can I take someone else’s hard work from Wikipedia – though it’s probably lots of peoples light work – and paste it into Google’s Knol, add some adwords and make a huge steaming pile of cash? Not likely.

From Wikipedia, GFDL (Text of the GNU Free Documentation License (GFDL)):

“You may copy and distribute the Document [wikipedia article] in any medium, either commercially or noncommercially, provided that this [GFDL] License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this [GFDL] License.”

As for modifications:

“You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it.”

There are further conditions for modified copies, see the GNU Free Documentation License (GFDL) for more information.

So unless you have separate “private” permission from each author of the content of a Wikipedia page (unlikely!) to mirror the content then you can’t do it. That is if the work is effectively released somewhere other than Wikipedia under a separate license then you may have rights to use it here. Otherwise no.

If you’re feeling cunning you might try overloading a CC-BY license with the GFDL by including it in the page, but I think that would contravene Knol’s ToS.

GFDL is quite clearly not compatible with copying from Wikipedia to Knol unless they add a license option of “GFDL” to knol.

IANAL, this is not legal advice; posted on Knol