I have a habit of writing small, reusable components in my spare time. I reuse these components with my clients' code bases. It occurs to me there's a potential issue that using identical code for multiple clients may bite me back in the future. I don't care who uses the code. I just don't want a situation where one company tries to sue another for copyright infringement due to my actions.

I'm not familiar with common licensing schemes. What do I need to specify in my code files to indicate that these protions are copyrighted to myself and usable by anyone, while differentiating them from the code specificly written for the client? Where can I find more information on this scenario?