Per their wiki - > The operating system originally called VAX/VMS was renamed to OpenVMS around 1991 to reflect the high degree of support for industry standar

Per their wiki - > The operating system originally called VAX/VMS was renamed to OpenVMS around 1991 to reflect the high degree of support for industry standards such as POSIX. > This prefix is now generally regarded as silent by OpenVMS users and developers calling the operating system "VMS". https://wiki.vmssoftware.com/OpenVMS https://wiki.vmssoftware.com/OpenVMS