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.
Thord Daniel Hedengren is a designer, writer, and blogger, and also the former editor of The Blog Herald. He used to be a hotshot in the gaming industry in Sweden, but sold everything and went International. Most recently he wrote a book called Smashing WordPress: Beyond the Blog, and does loads of kickass design.