The ebuilds in this overlay have mostly been taken from the Gentoo bugzilla, where the packages haven't yet made it into the portage tree. There are also a couple of version-bumped packages, and packages to install homegrown software on local machines. Feel free to use these packages, but do so at your own risk.
You can install this overlay using layman. Add the the
Sihnon overlay url
to your overlays variable in /etc/layman/layman.cfg. Then update
the list of overlays with layman -L and add the Sihnon overlay
with layman -a sihnon.
The contents of the overlay can be browsed in the Sihnon Git repository browser.