> POSIX was supposed to be popular to the point of default way that apps were written. It failed.
So POSIX was a long series of attempts to codify baseline Unix practice that arose because in the '87 time period there were tens of small, warring, incompatible Unix distributions ( cf. http://www.ugu.com/sui/ugu/show?ugu.flavors ), and systems software vendors could not write software that worked across all of these platforms properly.
The original post report is a cri de coeur call to action written in POSIX magazine attempting to oversell the story with a clickbait title in order to urge further POSIX work. This thread and others is loaded with people that have only read the title and have their own half-formed opinions.
There was never any idea that all apps everywhere would be written with POSIX. That's a ridiculous reading. I was there at the time. It was just an effort to get all of the Unix vendors on the same page so that the big commercial non-Unix OS vendor and their salespeople wouldn't eat the lunch of the high end workstation and server market.
And it succeeded phenomenally. With POSIX as a more-or-less stable substrate, it became possible to run, e.g., gnu's entire platform on almost anything that was POSIX-compliant or close; e.g. SunOS, Solaris, and eventually Linux, with minimal effort. It became possible for software like vi, emacs, mysql, sqlite to exist. Sysadmins could write shell scripts without anything like the kind of portability fear they had in the past.
Uncoincidentally, this continues today; all of the non-Windows software you're using is based on POSIX standards. Every phone is packed with POSIX-foundationed databases, daemons and sometimes even userlands. And of course there's Linux which, despite the continuing efforts of Red Hat, is about as POSIX as it comes.
Read the box at the bottom of page 9 of the original post. POSIX won, totally and unconditionally.