It wouldn't be hard to convert it over to another language, though the problem with the current design isn't the programming itself.
Has far more to do with the fact of relying on the built-in VB6 command structure. Converting across to .NET would definately solve quite a few problems, but you would be looking at completely recoding it from the ground up.
Problem with that would be in order to make it useable by everyone you'd need to make it using .NET 1.1. While I don't doubt someone can achieve this, making it stable and as lean (heh yeah who'd think you'd ever see those words related to the next) as VB6 then it requires one hell of a lot of skill on the programmer.
A good point if you can code it visually for the most part. I would also highly recommend using XML instead of ActiveX CodeMax to create your IntelliSense with.