Well you cant do anything about it. As per almost all bounty here in bitcointalk they are stating that they can change the rule when needed and its all up to the team. What I can advise you is better look for a reputable bounty manager who review the project before engaging in it.
As per almost all bounty here in bitcointalk they are stating that they can change the rule
what rule ? every bounty do always have the same rules .
I can advise you is better look for a reputable bounty manager
even the manager is reputable , they wont still assure that the campaign is legit because they are only working to manage it . they are not responsible for any payments .
to op , theres nothing you can do about it because they are the owners . if ever they turn onto scam youd better move on and try again your luck on other campaigns .