Hi! i've wanted to make a single-server type of game where every player plays in the same world to make a larger group of players at once.

i just dont know if i could do something like that.

The rule states "Players must be able to set up a dedicated server if there is not one available for the jam"

So as long as players can connect to your server, then you don't need to include the server in the downloads. But it is encouraged in-case your server ever shuts down or people want to test the submission offline/on a local network