reminds me of my own software I created and was selling online 20 years ago. I lost the source code but people still wanted to buy it. So I sold it for few years (shareware). I had a serial key generator for windows but it was annoying to do this manually.. I wanted to extract the key generation algo so it can be generated automatically after payment. I also tried many disassembly tools like ghidra, but without luck. I decided to stop selling / supporting the software. Nowadays, I still get the occasional mail from people asking where they can buy it, or of there are some updates.