You're still missing the point.
They volunteered themselves to help the game and players.
Toonslab actually wanted to pay the managers(and those working for years) in the first place. Snk even said it himself that he was given the opportunity to gain irl cash but he wishes to help the game out for free instead.
Look at the staffs, they all enjoy their roles because of powers and the kind of roles they have.
Since when did the game company itself made use of others just so that the managers/creators and slack?
They aren't slaves, their volunteers.