2.5 is something like 95% done. It's just missing bot debugging tools and multibot physics. But I abandoned it when it became clear that it wasn't going to be easily maintainable. At the moment I'm researching physics so I can be in a position to implement the more complex physical reactions correctly. Also, 2.43 has quite a few features added to it that the C++ source doesn't. On the other hand, the physics are much nicer in the C++ code.
When I start again it'll probably be from scratch using C#. I'll probably start with the physics and work the rest of the program into that. I should be in a position to start sometime in the next few months. If you want to start tinkering around int the VB source, you'll find it very easy. I actually learned VB working on this project.