OpenGL resides on the XServer. The OpenGL implementation is then required to be able to take commands from a remote device (the client). OpenGL itself together with GLX are part of the X-driver often enough. Pretending that it will just work is putting one's head in the sand; it requires heroic efforts to make a GL implementation take commands from a remote source. Compounding the pain is that many GL features do not even really make sense in this case; my favorite one being glMapBuffer, but there are others.
It shouldn't require any setup, beyond what is required for X itself and the OpenGL driver. To the driver, the X server is just another client.
Huh?!! AMD has released the specs to the GPU's (outside of video decode); Intel's GL driver for Linux is entirely open source. Lets take a real look at why it is not there: the effort to make remote rendering just work is borderline heroic. The underlying framework (DRI2) does not work over a network.
To be honest, I don't expect OpenGL with direct rendering to work well on Linux. It isn't a high priority for the hardware vendors, the hardware is complex, and the hardware vendors historically haven't been particularly open with technical specifications.