MMO Engines aren’t exactly something that are just lying around. Everyone who has ever made one has built their own from the ground up to suit their needs for map size, data streaming, polished netcode for player compensation, etc. A lot of engines available for third party use have basic netcode built in but you really aren’t going to be seeing large MMO numbers in those. It’s just the way things are. MMOs, due to their sheer size, require a bit more going into them than your average Unreal Engine 3 Indie Game.
