Great article. I especially liked the Stockholm-comparison about
sockets ;)

One thing I think is worth commenting on: 

> Plan 9 failed, in a sense, because Unix was simply too big and too
entrenched by the time Plan 9 came around. It was doomed by its
predecessor.

I believe this is wrong ;)

Afair, Linus himself has stated that he wouldn't have bothered with
Linux, had GNU Hurd or one of the BSDs – so: open source systems – been
ready at the time.
In 1992 there was a deep longing for a freely available OS / Kernel by
the hacker community, easily proven by the fact that RMS had founded
the FOSS movement with quite some success several years earlier.

If the Wikipedia article is accurate, Plan 9 was closed source in the
beginning, was shipped to universities beginning in 1992 (so roughly at
the same time as Linux).

> With source licenses costing $350, AT&T targeted the embedded systems
market rather than the computer market at large.


Linux was so successful not because Linus's first kernel was of such
outstanding quality or genius concepts (it was just a UNIX clone); but
*because* its source was freely available from the very beginning
(although it was not GNU-licensed until some time later).

So, I think I'm not too far away from the truth when I assume that
Plan9 might have become a huge success had they released it as a FOSS
project.
The same people who eventually joined Linux might have joined a Plan9
FOSS Community instead.

So, the great lesson from history for us is: Release your stuff as FOSS
;)


P.