Fair Use and Copyright are… more complex than it's probably worth going into - and with games, it's less well defined.
Fair use is fairly strict (and eroding), so since this isn't some kind of education project, it's probably safe to say that nothing we're doing falls under fair use.
At best, without exactly duplicating anything (with or without credit), we might be looked at as a derivative work.
But as I said, with games, I'm nowhere near certain (and I'm not sure anyone really is). Rules are (likely) not copyrightable - but their format, design, layout (race layouts, power layouts, class layouts), and all of their "creative" content (fluff, names for game elements), are almost assuredly fully protected.
Lets see - some potential trademark issues, as well (though that wouldn't be the core of it).
Anywho: Crazy rant over! It may help me look less crazy if I say: Totally studying for the Bar at the moment, having graduated from lawschool over the summer (with a particular interest in copyright/trademark - though I can't find a job in the field).