If 2 player..using 2 different pc. but stay in one house or play from same office.. is it legal to play and fight just like any other player? maybe also use group and help each other in same fight?

Also to trade each other?

The ip is same..but its 2 player 2 character..its not multi at all..
Second reason if this is illegal what will happen with player who is like aol.. i think its american online where people used to have all same ip but thousands of different pc.

Please clarify this to me dear admin.. thanks.