I have found this:
http://www.cse.ohio-state.edu/research/graphics/isotable/
Since there are very few open source isosurface generators I think it is worth
to look at it.
Wishes
Armando
Dr. Armando Navarro Vazquez
Facultade de quimica
Organic Chemistry Department
e-mail: qoajnv@usc.es
http://galileo.usc.es/~armando