Title is somewhat misleading -- this isn't really a leak, considering anyone with a developer build of the phone (available from T-mobile) could build the publicly-available source:

> Since Android is open source, you can easily download, > compile, and install it onto your phone. This requires > root access of course. Currently due to proprietary > issues, many things are broken running cupcake onto HTC > G1. Broken items include Bluetooth, OPENGL, and etc.