HDMI Over Cat5 Balun is just marketing terminology that some companies have used to define the same Hdmi Over Cat5 technology. So it's essentially the same thing as a Hdmi Over Cat5 Extender or a Hdmi Over Cat5 Wall Plate. Now that you can see the hdmi over cat5 balun example below:
This product works the same as the other technology as I've mentioned before. If you click the above link you will see techniqual details that how the technology works in the room.