Add an xml file containing this:
<?xml version="1.0" ?>
<repositories version="1.0">
<repo priority="50" quality="experimental" status="unofficial">
<name>chaos</name>
<description>Chaos.</description>
<homepage>https://github.com/travisghansen/chaos/</homepage>
<owner>
<email>travisghansen@github.com</email>
</owner>
<source type="git">git://github.com/travisghansen/chaos.git</source>
</repo>
</repositories>
to /etc/layman/overlays, say as "chaos.xml". The .xml is important by the way!
Then simply sync your layman overlay list, add the overlay and emerge the package.
layman -S ; layman -a chaos ; emerge unifi
Optionally, you can modify the port that the server listens on by editing /var/lib/unifi/data/system.properties .
I set my ports as such:
unifi.http.port=80
unifi.https.port=443
Update: script form
mkdir -p /etc/layman/overlays/
cat <<EOF >> /etc/layman/overlays/chaos.xml
<?xml version="1.0" ?>
<repositories version="1.0">
<repo priority="50" quality="experimental" status="unofficial">
<name>chaos</name>
<description>Chaos.</description>
<homepage>https://github.com/travisghansen/chaos/</homepage
<owner><email>travisghansen@github.com</email></owner>
<source type="git">git://github.com/travisghansen/chaos.git</source>
</repo>
</repositories>
EOF
layman -S ; layman -a chaos ; emerge unifi
cat <<EOF >> /var/lib/unifi/data/system.properties
unifi.http.port=80
unifi.https.port=443
EOF