Just wondering :3 Is this version only a demo with Steam gaining the updates?

this version on itch is a singleplayer demo, the steam version has multiplayer and such.

The Steam version also has more content available as well as some balancing.

If anything, I'd say the Itch version makes a good demo to play if you want to try it before buying it on Steam.

https://itch.io/t/4313357/demo