Valves Source engine supports both OpenGL and DirectX, OpenGL is used on Linux and PS3 versions.
The PS3 uses OpenGL wrappers.

And you can use both together on a PC, you can use DirectInput and DirectSound while using OpenGL.

Valve has also proven that OpenGL runs faster on Windows and Linux machines than Direct3D.
http://www.extremetech.com/gaming/133824-valve-opengl-is-faster-than-directx-even-on-windows