There's an interesting discussion going on right now about the effect of using GPL'ed fonts in a document. Some users on the Scribus list were concerned that using GPL'ed fonts in a document might subject the document itself to the GPL what with the GPL's greatly-exaggerated "viral" properties.(There is also the question of whether or when a font is actually software or not, but I'm not going to try to tackle that one right now.)
The Free Software Foundation (FSF) has weighed in on the discussion, and the response should (mostly) put people's minds at ease with regard to fonts available under the GPL. According to Dave Turner, GPL Compliance Engineer, a document with embedded fonts might be subject to the GPL, but it does not mean that the text of the document is. Even then, Turner says that the FSF was "unhappy with even this amount of influence for fonts, because (a) it's rarely what font authors intend and (b) it's possible that some applications do embedding behind the user's back." This attitude belies the portrayal of the FSF as an organization out to suck up all of the world's intellectual property.
The FSF also has an "experimental" exception to the GPL for fonts. If one is going to apply a software license to a font, however, it might be more appropriate to use the Lesser General Public License instead, which allows "non-free" programs to use a library, but still requires changes of the licensed software to be governed by the LGPL.