Its in-game. No additional download or purchase. If you cant find it ill look in my game to double check, but im pretty sure i saw it because i purchased it fairly recently and had it on during a lan game


Edit - oh, you mean after this 10 dlc patch, i have no idea how this is handled. Theres a few things gog needs to iron out. Maybe gog will clarify on monday. Or you could check in-game because thats where it was pre dlc