Thus, the CD key became a proxy for trust. Lending a friend your Opposing Force CD key was like lending them your dog tags. It was a bond. It said, "You can play as me, but don't get me banned."
: Before Steam, Valve used the WON (World Opponent Network) for multiplayer. When WON was shut down, players could use their original retail CD keys to "digitize" their copies by redeeming them on Steam. half life opposing force cd key