Man Fat.Clown why so angry? Plus you realize when he says it might not work he could mean that literally not just hey that might be illegal. Some games won't work online or through LAN if you don't have a extra cd key. Yes easy enough to get around on LAN but there was no mention of a extra cd key or if it was LAN or internet.
To the OP - Basically you will need another CD key if you want to play online just incase you didn't know.