Even he did pay half of all participants, it's still fall to scam if he didn't want to pay the participants when they're eligible.
It is still their campaign and they have the right to decide who is eligible and who is not. So neither you nor I can say who is eligible.
The campaign is confused and badly set up, it is to be expected that it will cause a lot of controversy. It's simple, if you're not ready to take risks with this kind of campaign, if you don't like the management, don't apply.