Not true. Joakim Sindholt is working on the open source Direct3D 9 state tracker _for Linux_ (the VMWare's one works only on Windows) and I think it's a matter of time until someone else starts working on other versions of Direct3D.
If someone wants to have an open source dx tracker he could build it ... and it's not said, that vmware won't opensource this driver after a while ... when the commercial benefit of closed source is gone they have no need or interst to keep it closed.
Since the D3D state tracker Zack is talking about is Windows-dependent,
it's not, but D3D-apps are windows-dependant in ways that gallium cannot solve. Hence it'd be absolutely useless to run the D3D state tracker on linux. Even Wine doesn't want one.
Still, closed source? I guess they're afraid that virtualbox/KVM/others use G3D for 3d-accelerated windows guests, thus stealing vmware's new killer feature. That's only fair after vmware spent all the money, but still sad.
Direct3D is a closed source library on top of a hardware driver. ATI and nVidia are implementing a driver that is used by the library. A Direct3D state tracker would probably not re-implement the complete Direct3D library, so this state tracker would be windows only.