Reading this article over on the FSF blog makes things look promising for gNewSense. gNewSense is a Linux distribution that has removed any code or blobs (binary firmware in kernel) that isn’t released under a free software compatible license.
SGI reccently released an updated version of its SGI Free License B which a large majority of OpenGL code in the X11 and Xorg implementations come from. Previous versions of this license weren’t compatible, but this new license is. So it looks like there maybe full OpenGL 3D support in Linux that is completely free.
Read the article.