I actually asked "Eddie" from Stake.com during his weekly stream about the "friend" that opened a very similar casino to Stake.com and he said "not that I recall" ....but he also said that they are not too worried about sites copying their concept and that it was actually flattering that other people were doing this. (I guess, if you are printing money like them, you would not mind a lot if people copied you)
There are not a lot of big casino software developers out there, so I figure some people just buy a white label casino template from these guys and they just change the color scheme a little to fire up a new casino.

I think I have to agree with Eddie, the biggest compliment is imitation, but they can only imitate the design or part of the concept but what will separate the leaders from a copy is the reputation they've established and the name the gamblers can associate themselves, ok let's say you are playing in Stake.com, and you sign up and play on a casino that copies Stake.com you will still feel that you are on Stake but you will not feel that you are comfortable playing on imitated casino, because you cannot just give trust to a new casino, just like you gave to a casino that you've played for a long time.