One of Android's biggest selling point, if not THE biggest selling point was the fact that the operating system was going to be open-source. Being open source may or may not make a difference in consumer's minds but with developers who have that need to tinker and improve, well Android is the place to do it.
Google has released the full source code for Android available to download NOW. With the release of the G1 and the world's introduction to Android just right around the corner, now is as good a time as any to make good on the promise to be "open". Game on, Android.