I think that would be out of scope, and too costly
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.