But does it mean bustabit won 100BTC or they've been distributed among other players?
It goes into the bankroll. The bankroll is owned by people who have "invested" in it (everyone has a stake, which represents what % of the bankroll they own). Bustabit itself charges 50% of all the bankroll-profits when ever it exceeds the historical "all time high" profit.
So a worked example:
Say the bankroll is 1000 BTC. Then someone bets and wins 10 BTC. They win from the bankroll, so the bankroll is 990 BTC. All investors stake remains the same. Now someone bets and loses 100 BTC. The bankroll would normally go: 990 + 100 = 1090 BTC. Except bustabit (aka Daniel) will want his cut. So he'd take 50% of the amount it's exceeded the historical highest profit. So in this case it'd be 50% of 90 BTC = 45 BTC. So the bankroll will actually increase by 100 - 45 = 55 BTC, i.e. the new bankroll will be 990 + 45 = 1035 BTC.
So in summary:
When you invest or divest you get a % ownership of the bankroll (which adjusts other peoples % ownership). When players win, they win from the bankroll. When players lose, they lose to the bankroll (and bustabit's commission).
People only need a license if they use bustabit's actual code. Bustabit made the old version opensource under a restrictive license that requires you to keep any changes you make also open source, and had an option to buy a license that allowed you to make changes without needing to make them also opensource. Many people however just use code and don't abide by the license, or use the actual bustabit code but try pretend they're not.
It was maybe a mistake, but bustabit never tried to control the game-concept (i.e. there's no patents or anything like that), just a copyright on the actual code that bustabit uses. Think something like lord-of-the-rings. If you want to write a book about elves and orcs and shit you don't need permission/license from Tolkien's estate. But if you want to actually use his words, you do.