Every time you write an open source project, you should license it so that other people should use the code. I’m not going to tell you which license you should use because that’s a matter of great flamewars. I’ve written a very simple utility called licenseme to put a license in your projects.
It’s really easy to run, just pass it a list of the names of contributors and their email addresses and it’ll generate a license for you of the specified type. I use this in all my projects that I open source because, like I said, people need to know under what terms they can re-use your code.