The NoVGUI.dll is essentially a wrapper DLL (that only wraps one function necessary to initialize the client display). In order to do a wrapper DLL, you'd have to use MSVC to build it (since MSVC is the only one that can handle VGUI.lib) and export all the functions with standard C linkage (plain non-mangled names). This would destroy the C++ aspect of the VGUI library (since you don't have classes with standard C). Destroying the C++ aspect of the VGUI library would make it kind of pointless as a mod feature since it would be difficult to create new (custom) VGUI windows.
It might be easier just to create your own VGUI library and re-implement all the work that Valve put into the VGUI library (there are MANY Linux GUI libraries that you could start from that are open source), but this would take quite a lot of work and wasn't worth it in my opinion.
And it's worth even less now that you can download the MSVC command line environment (.net 2005 beta) for free. If you don't want to compile using Microsoft's tools, because you don't like Microsoft, just keep in mind who's operating system you are running the game on anyway.
botman