Gambling is a bad deeds if you're a Muslim, if not there's nothing wrong with gambling.
There's a difference between pure donation and donation with gambling, in pure donation, you can't expect you will get a lot money because most people simply don't care with other people's lives. While gambling, many people like doing that, it's why some people ended up being an addict. Hence, this might be the reason why they created this project. There's no donation addict.
Yes, gambling and donation are the opposite. One side of gambling is to win money when playing. One party voluntarily gives the money they have to the other party.
I think this is a disguised activity, attracting people to gamble online. I do not believe that there are gamblers who want to lose to donate to charity. Everyone wants to win and win a lot of the money they bet. And the creator of this project doesn't necessarily want to donate to charity. Everyone has the goal of making money as 'players and project creators'. No one intends to do charity.