How would one protect their module?

I've been making some private modules and selling them for some robux but they always seem to get leaked, how are people stealing them and how can I prevent this? I've changed the require number to hex and put script.Parent = nil on all of the scripts as well and they still end up getting it? Any ideas?

Bytecode obfuscation scripts maybe, i don't know how to it, but looks like someone is stealing famous games too, using the website.