What Article System used by Vbulletin.org?

First, a significant percent of vBulletin.org's modifications are released, check Princeton's profile for a majority of the front-end modifications the community utilizes.

Secondly, this site is about promoting and hosting free modifications, however, at the end of the day - this is a still a community with custom code that will never be released for a few reasons:

1.) It's tightly integrated into our code base and some aspects were not originally coded by the current staff...releasing it would not be an option.

and

2.) vBulletin.org may be the official vBulletin modification staff, but we still have competition so some things we keep custom to benefit the community itself.