OpenGL on opeating systems with xlib only

I have written a browser for process visualisation (http://pvbrowser.sourceforge.net) that also uses OpenGL. It should run on several OS. Currently Linux/Unix and Windows. It should also run under OpenVMS. I think for that there should be a software mode OpenGL library on top of the xlib.
Can somebody tell we if such a library is available and where to get it ?
Yours:
Rainer Lehrig