From what I see, I don't think they are a scam perse, only that they changed the rules overnight, without any kind of consultation, although many bounties have that kind of disclaimer before one participates, it's still pretty scummy on their part, thus affecting their helpers.
The project may be genuine, but the team may be foul!
It is impossible to create a good product by bad methods and at the same time having a damaged reputation. It's my opinion.