I would imagine this is the case, otherwise he probably wouldn't have been willing to attach himself to the brand.  I'm sure he's being paid for doing these streams (maybe through referral links on occasions) but I'm also sure he has so much money that if he feels like dropping a million dollars into Stake because he wants to gamble more, he can do that.  I can only imagine the rewards he's getting from his massive volume as well as all the referral money from his fans.  It would be interesting to learn just how much money he's made from his partnership with Stake, but I imagine it's more than any of us think.