You'd have to say which cards they are. OpenGL 3.0 is basically synonymous with DX10, I believe (aside from not needing Vista), so I'd be a little surprised to see something that's DX10.1 compliant, but only supports OGL 2.0.
i7 2600K | ASUS Maximus IV GENE-Z | 580GTX | Corsair DDR3-2133
In translation it is Open Graphics Library. There is also OpenAL which is Open Audio Library. Those are the 2 main ones that you would see. OpenGL is just an API like DX but IMO behind DX especially DX11. That is probably why most games don't use it.