The site explains the process - it's profit from *bankrolled games*. It even specifies types of games (Poker) that don't count.

There's nothing wrong or unethical about the way it's calculated - it was all made clear up front.  But interestingly, he basically bet the viability of the casino on the price of BTC.  If BTC crashed after the ICO, the token would have skyrocketed in value in BTC and he'd likely have been at risk of collapse if he paid out all the BKB holders over time.  As is, he likely made a huge profit off the value of BTC over the last several months. This all assumes he kept the bankroll received in crypto.  If he switched it to USD, he'd have eliminated the risk/profits from BTC change, but also have a much smaller bankroll backstoppping the casino right now.