Do you think it is doable? Or is the package too Windows specific.
The main point of the DLL which is delivered with RDNZL and which is kind of a bridge between Lisp and .NET is the fact that it mixes what Microsoft calls "managed" and "unmanaged" code. Roughly, from the Lisp side it looks like plain old C code, and from the .NET side it looks like, well, .NET code.
AFAIU (but I'm not 100% sure), this can only be done with Microsoft's C++, and not, e.g., with their C# or one of their other .NET languages. There's surely /some/ way to do that with Mono because Mono is open source and you'll be able to tweak it somehow. However, I have no idea how to do that (and no time to do it as well).
Just wait a couple of months, I'm sure some GCC solution will popup :-) (apparently, there were some efforts in that direction in the context of Google SoC).
Michael.