[bb88]

> I also see that HP-UX, AIX, and Solaris are apparently still maintained and get releases, which suggests that they are still being used in production in some places.

When I worked for $(LargeDefenseContractor) we used Solaris for a defense system we were developing. Over time the older units (based on older hardware) would be passed down to the national guard. I would not be surprised if Solaris was still being used in obscure places in the military.

Solaris 7 was a pretty awesome OS as I recall, but pretty soon Intel and AMD started supporting linux as a workable OS option for their server chips. Then linux on the cloud took off and the rest is history.

[bsagdiyev]

Dated info (2001/2002?) but there was Solaris use at the NSA around that time too. Seems like the military and associated organs like to use it.