It was on VB4 until the new owners took over. They went back to VB3 as you can see.
VB4 is more complex to set up and maintain. Some don't want to bother with that. VB3 is a time proven stable platform that some find a lot easier to work with.
I've used both and am right at home with either one. Although my personal preference is 4.1.2. It's a real stable easy to work with version 4 platform. Besides that was the last version before they started messing around and consolidating the style vars.