RussCox? has ported a great deal of the PlanNineFromBellLabs functionality to *nix user space.
Plan 9 from User Space (aka plan9port) is a port of many Plan 9 programs from their native Plan 9 environment to Unix-like operating systems.
It includes the RcShell, and many other commands and file servers.
For a list of available programs, libraries and services see the plan9port man pages: http://man.cat-v.org/p9p/