The modification used here at vBulletin.org has never been released to the public and will probably never be.
The system was developed by multiple people over the years and it's roots go all the way back to the early 2.x.x vBulletin 'era'. It was not coded with easy installation in mind and lacks any sort of point and click install system; in reality it's based on some older code that has be re-written/fixed multiple times to work with newer versions of vBulletin. I'm sure if you look hard enough you can find code in there that was written in 2001.
My point is it's doubtful that this code will ever be released to the public. The fact that it's heavily integrated with all the other custom code at this site means that even if that did happen it would be a PITA to package it all up for use by the public. There is also the issue of all the people that have worked on it in the past who may or may not agree to having "their" work released. I don't even want to think about having to figure out who coded what in that rat's nest we call the modification 'database'.