Who does one get the hands on something like this? Just by accident or through an insider or is it possible to reverse engineer something like that? Sorry for the dumb question, I am a programming noob.
Could also have been one of the devs who leaked it. Lots of us keep copies of the source for stuff we work on, so they may have figured it's been long enough that no one would care if it leaked. However, I haven't looked at it yet, but I imagine it would be most problematic legally if it contained proprietary 3rd party code. Leaking that could land someone in hot water.