I can confirm that the keyboard was fully functional except for keys not producing character output. RaspberryPi with short-to-ground sensor under each key (so the keyboard would work as a mat with the keys removed if the horses didn't like them [as referenced in the BTS video]), running on batteries, making this the world's largest wireless keyboard. Measured 5 by 1.8m with the smallest keys being a beefy 29 x 28cm.

Source: Wife's uncle did the electronics and software for it.