If someone has a convincing and realistic plan to use the source code to MFI, I will attempt to make it available, most likely under a GNU-style license, but that is negotiable. The main impediment is the time that will be required to gather, organize, and document it. Including libraries, It is about 30,000 lines of C, plus about 10,000 lines of library code.
MFI uses about 4,400 lines customized from the commercial Quinn-Curtis Scientific and Engineering Library for DOS.
MFI is compiled with the Borland C 3.1 compiler, and uses the dynamic overlays manager provided with the compiler to overcome the 640K memory limit of DOS.
MFI uses several general purpose libraries that I coded, including a Uniform I/O library (written before ANSI C was published) designed to isolate higher level code from the operating system and hardware as much as I could manage. Other libraries I coded include a library of DOS functions, a DOS video interrupt 10 library to control the text screen, and a library of general-purpose routines.