Zero-K lobby uses Springie servers to run all games, it does not let you host your own game. When you create a new game, it will spawn a host for you. You have rights over such host, but do not have access to the !setpassword command that would do this. You can however !lock (and !unlock) the room, as well as !kick players you dont want to play, so you dont particularly need the password command.
We try to discourage people from playing 'closed' games, as it doesnt help foster community. Even if you just want to play with your friend, a lot of people, (usually developers) will want to spectate your game just to keep track of new player experience, help you with technical issues and teach you how to play. We cannot do this if the room is passworded.
