You can script vfp in any of the isapis. It's true you script VBscript in ASP and the .net languages in ASP.NET, but, can also use VFp as a scripting language.

I have never seen FOXISAPI used with mtdlls although in the notes in one of the versions of foxisapi(in the C++ code) it said it was possible. If that works, that would be the way I would go for performance and scalability.