The Bionic library is released under the 3-clause BSD licence while Dalvik, the virtual machine that Android uses, is again under the Apache licence.
This has been a point of contention between Google and the main Linux kernel development team due to differences in the way the teams wanted to make Android features part of the mainline kernel; it now appears that it will take four to five years for the two projects to come back to a common kernel.
Hence the only thing common to Android and any Linux distribution is the kernel.
The Android development takes place in a closed environment and source is released only when a release is complete. One cannot gain access to source while the development process is ongoing. There is no indication of when a release will be made. Google calls the tune and to hell with all models of open source development.
Neugebauer, however, points out that in the 1980s, the Free Software Foundation followed a similar model. "They released final releases with few intermediates, in exactly the same way that closed source products did at the time. The difference was that they provided the source code. Sure, it's a less common method of releasing code, but it's definitely not unusual," he says.
There are business reasons behind the mix of licences. The Apache licence allows Google to let others take the code and do what they want with it without the strictures which the GPL places on a piece of software. And the BSD licence is open slather - you can take code and lock it away after modifying it to your heart's content and nobody need be any the wiser.
In the case of Android 3, Google suddenly decided that it wasn't going to make any source available for the userspace bits. The kernel source was published. And that was that.
There is no guarantee that an Android device can continue to be upgraded as new versions of the OS emerge. Some devices are just cut off and if one wants to run a later version, one has to just fork out for a new device. For example, the Nexus One ran 2.1 and could be upgraded up to 2.3. And there the story ended.