"AGOL"? What is this? The Grauniad?
It's sad to see another of that pioneering generation heading off to the great operating system in the sky. However, I take issue with one part of this obituary: C is most emphatically *not* a "high level" language! I don't think Dennis Ritchie himself would thank you for referring to his "portable assembly language" as such.
Also, the history of UNIX through the ages seems more than a little revisionary: BSD Unix (which really *is* UNIX) and the BSD-derived NeXTStep were already available by 1991, long before Torvalds' kernel made it out into the wild as an integral part of a viable operating system.
I'd also disagree violently that Linux did anything to spread UNIX: Linux is no more "UNIX" than a Compaq PC *clone* was an actual IBM PC.
Linux is a *UNIX-like* operating system, but it is not itself a bona fide version of UNIX and has, therefore, done more to *reduce* the prevalence of *reduce* the use of Thompson & Ritchie's UNIX operating system and its later releases than even Microsoft have managed. Apple's BSD-derived OS X has probably done far more for UNIX's popularity in the consumer space as BSD really is a direct descendant of T&R's UNIX and not a clone.
This is analogous to Compaq's reverse engineering of the original IBM PC's BIOS, opening up the market for compatible IBM PC *clones*. Linux is a clone of UNIX. It is a "UNIX-compatible" OS.