This particular bonus is zero risk. You don't bet your deposited funds first. You bet the bonus funds. If you were betting your deposited funds, I'd understand being uneasy about this promo.
It isn't zero risk at all, because you say "Professional players or players considered, in our sole discretion, to be abusing the bonus system by any means may have bonuses revoked and be subject to further sanctions". You leave everything undefined, giving the player no recourse when you decide to keep their initial deposit. That's a significant risk.
Is it true? 5888$ registration bonus? I think it is not withdrawable ..
Yes, you can get a 3.01x bonus on your first deposit up to 888 BTC - that's a bonus of up to 2672.88 BTC, or over a million dollars. You need to wager the bonus amount 388x over before you can withdraw, and then you can only withdraw up to your 4.01x you initial deposit. You can cancel the bonus at any time and so long as you still have your initial deposit in your balance you can withdraw it, so in that sense it is risk free.
But see my previous paragraph - they reserve the right to subject you to unspecified "further sanctions" against you if they decide (at their sole discretion) that you "abused" the system in an undefined manner. They have already said that "playing at low odds" would constitute such abuse.
So in theory you have a tiny chance of clearing the wagering requirement and making a risk-free million dollars. But in practice they reserve the right to confiscate your deposit.
Be careful!
