Well, no, If you publicly release the source code to your proprietary software, people can download it and tinker with it, so long as they don't distribute it whether it's modified or not.
Unreal Engine, for example, has its entire source available free of charge online, but it's proprietary software and you can't make changes or use it to make a game unless you obtain a license from Epic Games (which is now free of charge in many cases, but you still have to go through the process of getting it).
Unreal Engine, for example, has its entire source available free of charge online, but it's proprietary software and you can't make changes or use it to make a game unless you obtain a license from Epic Games (which is now free of charge in many cases, but you still have to go through the process of getting it).