Marco Krohn was kind enough to email RMS on this fair use issue.
Marco asked:
While discussing (on the mailing list wikitech-l@wikipedia.org) the usage of "fair use" images/music a lengthy discussion came up if it is compatible with GFDL to use "fair use" images at all.
RMS responded:
If the use of these images is truly fair use, then it is ok regardless of what license you use for your work.
Whether this use of the images is truly fair use, that I don't know.
Marco:
This is surely covered by the "fair use" right of the United States, but is the resulting article including the citation still compatible with GFDL?
RMS:
Yes. I don't think there is really an issue here.
Additionally, RMS doesn't seem to think we need to rely at all on the aggregation argument, and finds that aspect of things confusing.
--Jimbo