Welcome (back) to Visual WebGui
7 years is a HUGE leap in terms of Visual WebGui and it's evolvement, and 7 years ago I didn't even know it existed, so I really can't comment on what changes have been made since that time. I notice however that you reference version 2.0.5701, which today does not indicate the actual version of the framework, rather the .NET version, or more precisely, the Visual Studio version it's intended for. This would to me indicate that you would have used .NET 2.0 (Visual Studio 2005) for this application.
As for changes that have been made to Visual WebGui through it's early stages and until today, then generally you should be able to use most, if not all, your standard code for the current version of Visual WebGui. If you have made any customizations, via a custom control or a Theme, you would have to redo all of them to be able to use it in the current version 6.4.x versions. This is due to the introduction of our Theme and Controls designer, and related changes in the runtime resource management.
We do have some documentation for breaking changes in the framework, but that documentation is not complete yet and it only documents the most general changes between version 6.3.x and version 6.4.x. You can find that article here. You can also find the general changelog here.
We will be happy to assist you through the process, so please don't by shy asking more specific questions on the problems you face through your upgrade process.