Do you have some more links? I did encounter "Vault" themed name in relation to HP-UX, but it sounded more like Trusted Solaris or similar MAC/MLS enabled unix version - but then I had literally a sentence or two for description.
Unfortunately not much much, given how HPE now kind of killed all the nice documents that HP-UX used to have 20 years ago.
This is what I can still find,
https://support.hpe.com/hpesc/public/docDisplay?docLocale=en...
Just to add a bit more of history, around 2000, HP starts pushing for HP-UX Vaults as means to also package application into production and restrict what resources they can use from the OS.