Just got a quote back from Rich Miner, "Member of Technical Staff, Google", about that non-fragmentation agreement that Google had all the members of the Open Handset Alliance sign to make sure that Android's code doesn't go forking off all over the place in a non-interoperable sort of way. It doesn't really add much to what we already know (I'm trying to nail down an actual copy of the text), but here it is:
The key thing here is that all members of the OHA have agreed to work to avoid fragmenting the platform. All OHA members have agreed not to fragment the platform and to use one repository as the main place for us to host Android distribution. This is independent of the fact that we use the Apache v2 license for our source code.
So thar ye go.