Quake3World

I want to just get Bustacap out and played by people. http://www.bustacap.vastserve.com I don't know which would be easier/better though, going with or without Steam Greenlight?

Since Bustacap is a standalone game and not a Q3 mod, I'm not sure how people will be able to browse for servers for it in the ingame browser since the engine is setup to still finds Q3 servers. What's involved in getting a server list for a new game/mod built off of the Q3 engine? Wouldn't it just be easier to put Bustacap on Steam Greenlight because doesn't Steam just have a server browser for its own programs so then the ingame browser in Bustacap wouldn't matter anymore?

I think you'd need to integrate Steamworks into your game to be able to use Steam's matchmaking services.

I don't know what (licensing) costs are involved with that or how hard/easy it would be to implement it in idTech3.

Quake Live (which is based on idTech3 engine) is on Steam. I don't know how much effort has to be put in implementing Steam's server finding mechanisms in idTech3, but it definitely is possible and may not be so hard to require a whole team of people to implement just one function in a game...