[Sparrow]

It's possible for NT to write properitary indicators and sell them, you can choose between giving someone your indicators as plain code or a dll. I am sure there are other more professional options available to lock down your code.
As for having someone code your strategy, the only thing you can do is have them sign a contract which would make it impossible for them to legally use or pass it on your system.

If someone is really determined and they've got the skills and access they'll crack your system/indicators, nothing is really 100% secure.