Is it possible to convert a dll library back to source code?

Not that I want to do this, but I need to outsource some non-critical parts of a software that I am writing, but I wouldn't want the other guys to copy everything that I have so far.

The code in the respective dll is not the whole code. I have managed to include only the necessary code in the library, but I still wouldn't like the other guys to copy my code.

Should I be worried?