This topic was discussed extensively on the Dexterity forums. You might try searching the archive for 'font legalities' or something similar.
In a nutshell: it depends, but if you're using bitmap representations, you're probably okay. If you want to distribute the actual font file, that's when things get more hazy. If you're simply using the fonts that are already installed on users' computers, then you're in the clear (though you then have the problem of selecting fonts that are on *all* of your users' computers).