Plan 9 is a distributed computing environment built at Bell Labs
starting in the late 1980s.  Plan 9 became a convenient platform for
experimenting with new ideas, applications, and services.

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.

WWW: https://9fans.github.io/plan9port/