1. Plan 9 was led by Rob Pike, Ken Thompson, Dave Presotto and Phil Winterbottom, with support from Dennis Ritchie and released (closed source) by Bell Labs ( https://en.wikipedia.org/wiki/Bell_Labs ) in 1992. In 1996, AT&T decided to deprioritize it. Lucent open sourced it in 2000 and free sourced it in 2002. It was a process-based OS where each process had its own filesystem (called a namespace) where each process could share virtual files (via 9P, later 9P2000, protocol) in the other processes' file systems. Like Unix (and Linux), files could represent devices. UTF-8 was used everywhere (since Ken Thompson invented it). rc was the default shell, rio was the windows system, plumber allowed system-wide hyperlinking, and sam and acme were the text editors.
2. 9front is a fork of Plan 9.
3. If you refresh the linked page (the main page for 9front), it has a new picture. There are a lot. Some are really bizarre, like the man in the wheelchair in front of the elevator. Others like the shot from Jurassic Park are funny and wrong- "it was a Silicon Graphics workstation (using IRIX, the SGI System V based Unix) running a three dimensional file system browser." (not Plan 9 which was not Unix) http://movies.stackexchange.com/a/9746