The MUD Coders Guild is doing a game jam again this year over on itch.io.
Enter the (Multi-User) Dungeon will be a 4 week long game jam running from April 17, 2019 to May 15, 2019.
The theme of the Second Annual Enter the (Multi-User) Dungeon Game Jam is: One-room.
Traditionally the space in a MUD was separated into Rooms which could be traversed one at a time.
One-room means pretty much what it says: there must be one room and only one room in your MUD. While loopholes and tricks might be used to somehow make that one room more than what it seems it must all take place in that one room.
See more about the jam on itch below: