Hi!
My name is Ayman Mahran. I'm a programmer and a web developer. I worked on multiple projects that involved using Google services APIs like Docs, Sheets, Calendar, etc.. for automation and data manipulation. I believe I can help you with this one. My solution is to deploy your app as a private add-on so that the script is not associated with the sheet. This way, your code can't be accessed by others using the sheet. If you're interested in this solution, please send me a message so that we can discuss the details.
Thanks,