Are those players with zero balances required to deposit their own money to fulfill the wagering requirements or can they wager the money they win as part of the free rewards system?
Not at all, the wagering target can be achieved by any means, including free rewards, tips and rains received.
However to unlock double, or 100% of the free rewards then a deposit is required. It could be crypto, fiat or game (CSGO, TF2, DOTA, RUST) skin.