The current production versions are 3.8.11, 4.2.5, and 5.3.1. v Bulletin 2 is no longer under active development.
When this version was released, it had numerous new features over v Bulletin 1, which it replaced.
v Bulletin 4 was described in this announcement as "an extensive rewrite of the v Bulletin system.
Architecturally, v Bulletin 4 follows MVC (model-view-controller) object oriented principles, allowing far greater capabilities in code re-use and extendability." At the time, the requirements of v Bulletin 4 were "PHP 5.2.3 and My SQL 5.0.22 or newer".
In August, we announced a major overhaul of the code base.
Kier Darby was brought on during the v Bulletin 2.0 Beta phase to further development.
The release of v Bulletin 2 proved to be very successful and is what made v Bulletin popular.
Improvements include private messaging between users, attaching polls to threads, unlimited forum nesting, user avatars, and a user control panel. Initially, version 3.0 was intended to be an extension of the 2.x release that would improve performance and user experience.
However, as time progressed, it proved to be a complete rewrite.