Which CD Key is being used when I play DayZ? I bought Arma II: Complete Collection($39.99) on steam, and I want to play on the same server with my brother. I heard that you can't play on the same server with someone else if they have the same CD Key. I don't want to buy the complete collection again. So would installing Arma II: Complete collection on my brothers computer through my steam account and then just buying "Arma II"($12.99) to obtain a new CD Key for my brother, make it work?