Frankly speaking I do not care about license, I would prefer to check the reputation of the casino in this forum first.
Why I do not care about license? First because most bitcoin casino started without license, there are even some trusted sites without license till these days.
Secondly, license does not guarantee that the site wont be a scam. Example, 1xbet/1xbit which is a licensed casino but it has very bad reputation here in this forum.
Last but not least, you can always check the validity of the license by the validator/validation page of the license provider.
One of the most used license is Curacao, it has validator where you can check the validity of the license of the casino that claims having Curacao license.
It makes sense. Sometimes fraudsters just take adavantage of their legitimate license to gain more trust from users, which eventually will be deplete since they have their plan to steal from their users if it happen that they accumulate enough.
The trust of users is way bigger than lossing reputation. I think it is just that some of casinos turns out to scam people because they already lose lots of money.