A commissioner is the person who runs a sim league: they create it, invite the GMs, set its rules, keep it moving and settle disputes. The job is the same one a fantasy commissioner has, with more rules to set.
In HoopSim every multiplayer league has a commissioner, normally the GM who created it. They advance the league (by hand or on a cadence of 1 to 7 league days per run), decide how many GMs must be Ready, pause or skip a run, and post a next-advance notice that hangs as a clock on everyone's screen. They move the offseason along or put it on autopilot, run the lottery and staff free agency rounds, review every accepted trade in a 24-hour veto window (veto, fast-track or reverse), set the trade deadline, decide whether AI GMs trade, tune sim and cap settings, invite GMs with the league link or personal invites, reassign or remove GMs, and send League office memos. A solo league has no commissioner: its one GM presses SIM.
Rulebook: The commissioner. Related: sim league, auto-advance.