This is the nature of C++ development. If you ship your code as a compiled object, you must ship the inline function definitions as source, and everyone will be able to read them. That’s what an inline function is–after all, the compiler has to be able to read it in order to inline it.
If that makes you nervous for some reason, the only way to avoid it is to make the methods non-inline. You can do that freely; there is no technical reason to make any of your methods inline, other than the performance benefits of inline methods.
But I don’t know why you should try to hide your code from people you are distributing it to. If anyone really wants to see what it is doing, they can always disassemble it anyway.
David