I have tried your script's demo game and I can see that you put efforts into creating a high quality product so I can understand your prices, too. You have your own costs, after all.
OneUI is a fine Bootstrap template and I appreciate the fact that you are keeping its credits in the code. Since it has a clean and smooth layout, I understand that it is the choice of many developers. Maybe, you could include the credits in the thread code, too, to make people clear that it is a layout that any developer can buy for his project and does not represent the script behind the scene thus the similar layout of different projects does not mean any relation between their scripts.
I have verified your method with the code in
this page and it indeed is provably fair. You wrote that I could test, but I also have not found any security issue on your server. These two things were only quick lookthroughs, though, so I cannot write a certificate about them.
Since you are writing that I need a Linux VPS and basic Linux knowledge to use your script, does your script not work at all on a Windows VPS?
What Linux distributions has been it tested on already?
Furthermore, I advise you to hearten your satisfied customers to write their feedbacks about their experiences with your product. It should not be too difficult if your script is really as good as I imagine it is. I think, that would hearten many members to become your customers.
