Good decision, if you ask me.

All reddit code is licensed under the Common Public Attribution License, which is basically the Mozilla license with a handful of changes. Specifically, the CPAL stipulates that when running reddit’s code publicly, any changes to the code must be made available publicly and the site must make clear that it is running reddit code.

Check out code.reddit.com for more, the blog post from which the above quote was taken, and the Reddit alien’s explanation to why they are doing this: