With Multics i'm familiar enough, i meant unisys specifically.

Not for free,

https://www.unisys.com/client-education/mcp-clearpath-server...

However you can get into the documentation for free,

NEWP manual, the systems language,

https://public.support.unisys.com/aseries/docs/ClearPath-MCP...

https://public.support.unisys.com/aseries/docs/ClearPath-MCP...

Overall documentation,

https://public.support.unisys.com/aseries/docs/ClearPath-MCP...

The original system back in 1960's,

https://en.wikipedia.org/wiki/Burroughs_Large_Systems