Is it possible to use VirtualGL without xdm, gdm, kdm, etc. ?
Sure. VirtualGL just needs access to the main X display, because that's the only way to get at the 3D hardware, but you could just as easily start a headless X server with no display manager or window manager on your 3D graphics card, create an xauth key for it, and store the key under /etc/opt/VirtualGL/vgl_xauth_key. vglrun will look for that key and, if the key exists and the user has access to read it, vglrun will automatically import it into the user's ~/.Xauthority file, thus granting them access to the 3D X server. If you only ever need to use VirtualGL under a single user account at a time, you can just use startx to start the X server, and this should give your account access to it.
Thank you for the reply. I have the following situation:
I have a computer with a video card and two TESLA devices and I would like to allow two another remote users to use the correspondent TESLA cards, while using myself normal video card with a display, is that possible?
It should be. I think the way you'd accomplish it would be to run a headless X server on each graphics pipe you want to use for remote 3D, then run a regular X server on the pipe you want to use locally. You might want to post on virtualgl-users, as there are some people who monitor that list who are more experts on setting up headless X displays than I am.
Thank you, again. I'll try to do that first alone. (There was one post in the mail list about TESLA with some hints.)