So, does that make AIX that last one standing of the original, commercial Unixen?

And by that I mean those commercial OSes that started with AT&T and drifted from there. Not to slight, say, the OpenSolaris children, per se, or the open source BSDs.

There were so many back in the day, with so many platforms and CPUs. HP, IBM, AT&T, SCO, Pyramid, Ridge, Sun, Sequent.

Perhaps there are still some overseas?

That’s sad. One of the first pieces of (serious) software I wrote was licensed by HP for bundling with it. Didn’t use HP-UX a lot but it’s a pity we’re asymptoting towards a Unix monoculture.