There _used to be_ an OS product called "HP Secure OS Software for Linux", which was a version of Linux with Mandatory Access Control and security compartmentalization systems added - a kind of "VirtualVault for Linux" if you will.
We used it in one project.
If I recall correctly, it was very much based on RedHat of the equivalent age, replacing only the kernel and security-critical packages with HP-extended versions.
It apparently failed to be profitable for HP, so the product was discontinued after a while. I guess the customers' point was "we now get SELinux for free in most major distributions, why should we pay extra for this?"
I was kind of sad to see it go away: the extended security system seemed pretty flexible, yet easier to understand than SELinux. (But that might be only because I had worked with HP-UX VirtualVault before... :)
