The application architecture and framework is basically the same as activecollab's 0.7.1
It seems like it was developed by Ilija, but unfortunately he didn't document it. Here is a
post at the activecollab forum about the subject.
On the upside, it looks quite well done, so it should be easy to figure out. As a matter of fact, I had to, in order to add the OpenGoo features. So, if you would like to discuss any particular issue, I could help.