If you are scared someone stole your business because they saw your source code a few years ago, then I argue you don't know what is the value you deliver. Code is one of the least important bits :)
https://intuitiveexplanations.com/tech/replit/
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A project or company is a system. Code is only a momentarily artifact the system produced. If that artifact is still all the value you have, the system is dead.
Of course there are exceptions. You can get rich by having a patent for some fancy crypto algorithm. Not my cup of tea though. Feels morally similar to profiting from a patent for a vaccine.