That's not particularly surprising to be honest. If it's a server operating system, on hardware that doesn't change, there's not really a reason to update the OS unless there's a security problem found
Apparently the latest VOS release was in 2025, which means that somewhere there's a team of developers maintaining it. That's really the thing I find the most interesting, that there exists teams developing operating systems like VOS, strange DOS clones or UnixWare (perhaps less so these days). Must be a strange anonymous life.
This perfectly characterizes most embedded systems work. Competent software development using bespoke or off the shelf components that are not mainstream. Nobody ever realizes they’re using your computer software if you’ve done your job right. One day someone throws your appliance away because it’s obsolete.