These ebuilds come from http://git.overlays.gentoo.org/gitweb/?p=dev/anant/plan9.git;a=summary.
If you have some problems, go to the official site first.
mk : Make equivalent for the Plan9 System ( http://cm.bell-labs.com/magic/man2html/1/mk )
plan9port : Plan9 Ported to Linux ( http://swtch.com/plan9port/ )
Add an ebuild in portage :
The ebuild is now in the portage tree.
You can also use layman : emerge layman then layman -a plan9
For Paludis use this rsync : rsync://gentoo.zugaina.org/plan9-portage
If you have a problem : ycarus(-at-)zugaina.org