I am not sure about this, most mods require you to have the source engine i think. I had it already so it just loaded up for me. I am not sure if it would have came with it if not. You can catch deals on steam at times and get CS:S or TF2 for $10. Orange Box (HL2 series, Portal, and TF2) is only $30, it is more than worth it IMO.
Ya i should have mentioned it is multiplayer only, but to be honest that is all 99% of the masses fell in love with Goldeneye for. I doubt most people would have even played through the campaign again. For today's standards the single player style, trial and error + memorization, is outdated and replaced with more intuitive based sandbox oriented gameplay.
Yeh you need to have purchased a source game to play it.