Valve has unveiled the source for the Direct3D translator in OpenGL

Valve opened the source for the Direct3D -> OpenGL compiler, putting it on Github . The code is provided “as is” and is not supported, but they (judging by the project page) accept patches. In this case, the code is unlikely to be assembled in the form in which it is laid out, and, in addition, it contains fragments written specifically for the Source Engine.
The translator supports a limited subset of Direct3D 9.0c, can translate HLSL bytecode to GLSL, and has some SM3 support.

Original news here: http://www.xakep.ru/post/62185/