It's no different from X11, which is also a protocol/spec with many implementations.
Maintained: Only for bugfixes, except by metux, who is working on starting a fork.
This isn't a big issue because Xorg splits a basic GUI into dozens of different daemons and services (compositors, window managers, input daemons) so it seems like there are different X11 implementations even when there's usually only Xorg.