From the latest update:

"""A lot of you have mentioned that we should open source everything if worse comes to worse. In fact, the code is already open, but if we cannot pull together to make this a retail product, we will absolutely fully open source everything, content and code and turn it over to the community. Actually, at some point we’d like to do that no matter what, even after a retail release (however many years later, when it makes fiscal sense). But right now the code is under the same modified BSD license as the Go programming language and the contents are all Creative Commons Attribution Noncommercial Share-Alike."""