In Haxball, the is automatically the owner . The owner has full control: kicking/banning players, changing settings, starting matches, and assigning admins. However, if the owner leaves the room, the hosting rights usually transfer to another player.
Modern OPMode often refers to a set of custom CSS and JavaScript overlays that: haxball opmode
Most "OP Modes" are not official HaxBall releases. They are usually: In Haxball, the is automatically the owner