Old article but removes any illusions about Google being a friend to open-source. I was especially surprised to learn members of the Open Handset Alliance are contractually obligated to only ship versions of Android approved by Google. Versions where most open-source components have been replaced by Google’s proprietary software. Acer was threatened when they tried to create a customized Android phone for the Chinese market. Something Android’s open-source license should allow.
TL;DR Google released Android as open-source in order to gain market share but now that they have it they’re replacing most of Android with proprietary software in order to lock in users and developers.
I look at the AOSP kind of like Sound Bytes’ IRC transition from EFnet to Dalnet. People were free to come join us on Dalnet, or still convene on EFnet if they wanted. The difference is, when Nick was still logging onto IRC, he would be on EFnet. People will follow the most significant person(s). Despite Dalnet offering a few technical advantages, unless you can convince the leader to migrate, most people will stick with the leader for many practical reasons. So too, you can load/run CyanogenMod, PAC-ROM, Paranoid Android, Omnirom, and so on. There are some projects, such as OpenGApps.org, to try and fill some of the gaps (relative to AOSP) in the alternate ROMs. But of course, using one of these altROMs will having you lagging features and fixes found in AOSP, as well as probably having to do more to keep your system up-to-date.
What I find interesting is that the trend for iOS is only very slightly trending upwards, whereas Android has such a steeply increasing share.