Yeah, but Atlyss was built from the ground up to be an online game.
It's often not an easy task to just jam online into a game that was never designed for it. The developer would likely have to rewrite massive chunks of almost every gameplay related script to both; get things syncing across clients and working with more than one player.
Not to mention, Archipelagates is a singleplayer game at it's core, and just slapping online into it with no considerations given to how this could effect the actual experience would be a poor decision, so parts of the game's design would likely need to be altered too, and it appears like the dev wants to wrap up development, not extend it.