I ran across this public domain isosurface / polygon code recently.
It’s just a polygon library (i.e., no OpenGL), but it’s from Jules
Bloomenthal and it looks very good:
http://www.unchainedgeometry.com/jbloom/papers.html
http://www.unchainedgeometry.com/jbloom/misc/polygonizer++.tgz
I think this might be the best solution to our need for surfaces.
Cheers,
-Geoff