Some questions about Steam: Do you have to install a generic Steam app before downloading games?
Yes.
Does Steam cost anything by itself (excluding the cost of games, of course)?
No.
Does it have any DRM on it at all?
You need to have Steam running to play games acquired on Steam. They're tied to your account, but you can install them on as many computers as you want, as long as you're only logged onto one at a time.