In that regard, Android would most likely fall in this category. So, in sum, the only question for google would be how to continue making it an effective tool to fend off competition in the search world. In this regard, the earlier article from BusinessWeek is quite relevant: https://lwn.net/Articles/435342/ It looks like they've effectively "forked" the code-base with little regard to the older way of doing things to get it to work on tablets and they will only release an ulterior cleaned-up tree that seamless merges the code-bases. They would have likely made it easier for everyone to understand if they would have not used an incremental number (i.e. from 2.3 to 3.0) but would have instead used something closer to what it really is: Android for Tablets 1.0. That would have been less confusing. It would also likely have made it clearer to everyone, including consumers, that it's not preferable to buy a phone running Android 3.0 than one running 2.3. Then again, maybe the issue was to keep branding continuity given the current brain-share "Android" enjoys ...
Regarding Amazon, I'm not sure it can actually "loosen" Google's grip and I'm not sure it would benefit from forking the code. The only thing that would really make a difference here is if someone had enough fire-power to fork the code and carry it forward *faster* than Google can. An organization would likely therefore have to have something of the order of several hundred engineers paid to do nothing but develop a forked Android, possibly in a more open, community fashion. The economics of this one just don't add up though. No one has the incentive of maintaining Android on that level as a moat as Google does. And no "community" effort could even remotely come close to the sheer engineering power Google is pouring into this.
So, for the foreseeable, we will likely have to make-do with Google's code-drops, no matter how frustrating these are. Unless I'm missing something.