So I have been using GLES on a Dispmanx EGL context for years now, with very good results. Until now, I have been using the default Raspbian GLES libraries, which I believe are closed binaries.
However, with the advent of these OpenGL drivers, which are integrated in MESA I believe, it should be possible to use OpenGL on the Pi, and it should be theorically possible to do that without X, on a dispmanx context just like with EGL/GLES.
But I have yet to see a piece of code doing that. Is it possible at all? I don't use X11 on any of my projects, so I hope it is...