Actually, I have no clue. However, very few games enable Multiplayer with the same copy. Those who do have a "spawn" version of the game, which Sins doesn't, i.e. an installation that solely works for multiplayer and usually only for a limited number of players (e.g. max. 3 spawns per original in the LAN-game). It'd sort of ruin their income if one copy of Sins enable innumerable players to use it via LAN, eh?
