Released earlier this year with eventual co-op play promised, sole Stardew Valley creator, Eric Barone, eventually drafted in help from his publisher's other teams to help speed up the process while he, still single-handedly pushed forward in creating new content for the main gain.
While still on schedule for release "early next year", a modder by the name of "spacechase0" has taken it into their own hands to enable a very rough-around-the-edges multiplayer function into the surprise hit indie title of 2016.
You and your buddies each get your own house, inventory and skills, but share things like wallet contents and even um... relationships. Now whether that's a technical hurdle to overcome, or simply a daring little venture from the original mod creator is going to be left to the imagination of the reader right now.
Want to get tilling the fields with a friend? Head over here. Just be warned that your partner may look like he's running all over your crops. They can't help it.