Radiosity is an approach to solve the global illumination problem. The simplifications it assumes are:
As can be guessed, these simplifications are made to enable the use of the finite elements method to solve the problem. The approach used is here is classical radiosity, with no use of funky basis functions or hierarchical methods. Form factors are computed with the hemicube technique and the whole solution solved with progressive radiosity.
The program was originally developed under DOS and it uses a software renderer both for viewing and computing form factors. Source code is lost, but luckily I have kept an executable. It runs under Windows and uses Direct3D only to output the already rendered image.