Toby wrote:
What!? how could this possibly be? Why would the GNU FDL be stricter than ordinary copyright law? If I quote a line from a biography of Winston Churchill in my own FDL biography, why must that be invariant? This doesn't make any sense to me.
Speaking only for text, you'd have an ethical (and, quite possibly, a legal) obligation to leave the quotation as-is; otherwise you're saying someone said something they did not.
That's distinct from coypright, though, which allows for fair use *but* each person has to determine whether they have the right to fair use; it's not a blanket license. E.g. I as an educator in school may pass the "fair use" test to show a film in class for free, whereas Joe Moneybags, who wants to show the same film for $10 in a theater without working out a deal with Paramount, would not.
IANAL,
kq