Well he and others moved away from UNIX, created Plan 9 and Inferno.

In these efforts they also tried to create successor languages to C, Alef and Limbo (for userspace), and never cared that much about anything past C89.

He has settled with Linux because that is the winner of UNIX wars, which predated Linux wars on Distrowatch.

As for the original UNIX,

"Using Unix is the computing equivalent of listening only to music by David Cassidy"

-- Rob Pike

Yes, Unix = Linux for all intents and purposes in 2026. When I started in the early 90s, there was a galaxy of Unices - SunOS/Solaris, HP-UX, AIX, and many others people people don't even remember (ConvexOS anyone?). Heck, back then if you wanted to run a particular software for your industry, you might have to buy and install a specific proprietary Unix.

Today? It's all Linux or Windows (of course, now also Web/SaaS). All these different Unices have fallen by the wayside in favor of Linux. Yes, some are still around but the mindshare has been in Linux for the last 20 years.

I suspect you could rip out a ton of autoconf rules and no one would notice.

Caring about which systems are branded UNIX is like caring about which NBA player was paid to endorse a particular brand of athletic footwear.

I've been using Linux for 30+ years now and have always considered it free (as in speech) Unix. For my purposes, the difference was always more legal and philosophical than practical. Of course, I was a student back then and didn't need to run the commercial software of the time.