It is like the DMX splitter, except it is for pixelnet. It has one input, a passthru, and two regenerated outputs. It works like the pixelnet output of an active or passive hub without the SSC ports.You can use it when you need to split a pixelnet run to two places and don't want to tie up a hub. It also regenerates the signals so you don't run into issues with too many pixelnet hubs or devices on a cable.
Trying to avoid the engineering technobabble, it all depends on how lucky you are... The split itself is going to introduce an "impedance mismatch" in the wire which will cause reflections of the signal and distortion. If you are lucky, it won't be a problem. If you are not lucky, you will get errors in the transmitted data. Since we use one way communication, there is no opportunity for corrections to the data errors... If you want to dig deeper, you can explore transmission lines and smith charts. However, you don't need to know any of that stuff to have fun with blinky...
There's no firmware involved, since there is no micro on the board. I haven't tried it with DMX, but I think it would work. /mike