This is one of the modules used in the Approval process automation extension for iTop.
Release packages can be found on the iTop Hub Store. This is the best way to get a running package as those contains all the needed modules and stable code.
When downloading directly from GitHub (by cloning or downloading as zip) you will get potentially unstable code, and you will miss additional modules.
This iTop module development is sponsored, led and supported by Combodo.