In the few days since VOGL was opened up on GitHub, there's been many commits landing. Of the Valve developers, most of the VOGL work seems to be done by Rich Geldreich and Mike Sartain but already there have been improvements landing by other open-source Linux developers.
As Rich Geldreich blogged yesterday, this open-source OpenGL debugger also now works for the AMD Catalyst Linux graphics driver. Most of Valve's development still happens on NVIDIA Linux systems with AMD's Catalyst still being a thorn in the side of Linux game developers. Rich wrote, "I fixed a number of issues specific to AMD's driver."
I should have more VOGL debugger details out next week during GDC.