It's not my kinda thing, and I'm too late anyways, however, I just wanted to pass on kudos both to the OP for offering a freebie, and also to the guys who made the game.
What an incredibly sensible idea, and it's amazing it's not done more often.
If you're making a multiplayer game, why not release it with 2 or more licenses per purchase, to encourage people to play it? They seem to have noticed this, and it's a great idea.
Of course, tougher on hard copies, but really, it wouldn't cost much to include 2 dvds in a case instead of one, now, would it?
Strange that it always seems to be the small indie companies making these moves, while the larger ones just seem to keep on removing content (for future DLC) and locking down their games ever tighter with security.
Maybe I've got my head in the clouds, but I'd guess it's perhaps that the smaller devs have more interest in seeing their game get played and enjoyed, over pure sales stats.