There are renewal charges and having an license is costly task and there are lot of other implications that needs to be fulfilled but most of the casino first of all go for license as players search for the details before joining any casino like us.So at this time Curacao license is the most famous and somewhat cheap at this time so you will find most of the casino operating under the same license.But after that they can turn out to be scam also so make sure you play over legit casinos only.
I believe that getting a curacao license is just throwing money out the door and nothing more. As I have said before, it is a useless one since there are places with no license at all and still managed to become huge, so why would anyone imagine that would change?
If you are spending a lot of money for a license, and you are spending money to fit the license requirements and even hiring lawyers and such to keep it in check then I am sorry but you are spending money that you do not have to spend. In fact instead of spending money on that, if you spent that exact amount on marketing and just give people money, competition or promotion or bonus or challenge or whatever then you would probably be doing better.