Possible Duplicate:
Is it possible to play two different Steam games on the same account at the same time?
I recently heard about Magicka and I really want to play it. I told my friend about it, and so does he, but we don't really want to buy it twice (we would prefer to pay for one copy and just play from that). I know that I can download a game that is in my Steam library, and I wanted to know if he could play it on another computer if I were to buy it.