It's important to note that this is them moving in-development branches/features "behind closed doors", not making Android closed source. Whenever a feature is ready they then merge it publicly. I know this community tends to be filled with purists, many of whom are well informed and reasoned, but I'm actually totally fine with this change. This kind of structure isn't crazy uncommon, and I imagine it's mainly an effort to stop tech journalists analysing random in-progress features for an article. Personally, I wouldn't want to develop code with that kind of pressure.
Not only that, the Android Police article mentions they had a lot of trouble merging the internal branches and the public branches, so I’m guessing as time went on they’ve diverged more and more.
Boiling the frog, slowly... As more of these terrible decisions keep stifling Android up to a point where it becomes just a vessel to Google's proprietary garbage (as it has been the case for many years already for a lot of things), it should be a wake up call for mobile Linux to keep improving and do it faster.
I don't know anything about Android AOSP, so I found this clarification important:
This does not mean that Google is making Android a closed-source platform, but rather that the open-source aspect will only be released when a new branch is released to AOSP with those changes, including when new full versions or maintenance releases are finished.
Yes, there will still be the aosp repository as open-source. It will have some lag, but still there.
Thus said, Google has moved a lot of things into the Google Play services over the years (closed sources).
So, who knows what's next!
Let's praise that some companies inject money / devs into postmarketos!