Ask HN: How was the Kinect hacked?

I've been seeing lots of cool videos on what people round the world has been doing with the Kinect hooked up to their PCs.

My understanding about the way 'hacked' is being used around here is that people have figured out how to hook up the Kinect to a PC and write software to utilize it.

My question is then, when you get a device like the Kinect, what's the process to hack it such that it can work with your PC? How do you understand it enough such that you can write your own driver?