I bet few people ever used it, but I actually did for a short time. There has been an X11 / "regular Unix" implementation of #OpenStep besides GNUstep: for Solaris (Sun's OS at the time).
http://www.kevra.org/TheBestOfNext/NeXTProducts/NeXTSoftware/OpenStep-SolarisWhitePaper/files/page538_1.pdf
@helge Was there ever a version of OpenSTEP for Solaris that was compiled as x86 (or ppc…) binaries as the diagram seems to indicate? So far, I’ve only seen the Solaris/SPARC version.
@me_ I’ve used it on x86. I wonder whether I could find the install media for that. It was a long time ago and I don’t remember how I installed it.
@helge Interesting, I would be very interested in obtaining a copy if you still happen to have one. The only versions available now are based on the SPARC version (https://github.com/itomato/lubu and https://archive.org/details/open-step-entcd) AFAIK. The Enterprise version was also available for HP-UX on PA-RISC…