Hm, I just did a few quick google searches to try to help out, but no luck. I thought I remembered an actual promo CD they released way back in the day with a few licensed songs by bands, but you'd think that'd show up in a search. I may have lost my mind. *Dances the crazy-dance*
What I could find is that the title theme song is credited to Craig Hazen, Julie Dansky and David Wolfert, most likely just career songwriters for various media I guess.
But yeah, from memory there were a couple of actual "song" songs used, in addition to the theme written specifically for the show.
