Earlier quoted context omitted.
Already does? “The OpenPush project aims to create ... Development is still ongoing.” Doesn’t sound like it from the website.
It is already usable. Nobody would claim that a Linux distro isn't open just because it doesn't have a built-in push API. You can build one on top for other apps to use, and you can do the same on Android. This is notably different from iOS.
The repo says it is unfinished, and commits seem to have stopped a year ago. It looks like it has been abandoned.
Has it been used in production somewhere?