ay man, you do you, im not a lawyer, good luck

im not a gamedev per-se, but in my opinion based on what i can see:

1. give them ownership: maybe make a part or the whole game open source, to make sure they have something in return
2. make them a part of your game: have characters or story based on your communities shenanigans?
3. build a strong community: memes, active and kind mods, reports, you know, communities.