Kinda the other way around, the NonStop kernel can present a Guardian personality or an OSS (Open Systems Services) linux-like compatible personality. The OSS layer is basically running on top of the NSK/Guardian native layer but allows you to compile most linux software.
No, I meant the other way around. I don’t know to what degree it ever got released, but he spent years getting it to work on “commodity” mainframe hardware running Linux, as HP wanted to get out of the business of maintaining special equipment and OS just for this customer.