~snip~
From what I know, most gambling sites get their slots from 3rd party software providers. They are not buying the source code, they are just renting the slots. Yes, there are sites that hire developers to make unique slots for them exclusively, but usually those slots look "too simple", you could say, in comparison with those they could rent from the top software companies for online slots.
If you know at least one case when a gambling site bought the source code from a big company like NetEnt or Play'n Go, please share a link. I'm interested in this kind of stuff.
If they rent the source code for add on their site, they will not have to spend big money to buy the license. But perhaps, if the gambling site rent the source code from the famous software provider, I think the cost will be higher since they always maintain their product. If the developers have more experience in the gambling business and that person has a new idea about slots games, he will create new slots games from scratch.
I don't know a gambling site that buys the source code from the big company because I never search for that.
Well, I have searched for that, and found no results. That is because it's pointless to pay big money for buying a source code, not knowing whether it will be profitable, when you can just rent the thing, and see what happens. Besides, I doubt that any major online slot providing company will sell their source code, in the first place.