Is a kitchen display screen included, or is it another purchase?

Included. A kitchen display system here is a device you pair as a screen in the kitchen, not a separate product with its own price. An iPad, an iPhone, an Android tablet or an old Android phone will do, and there is no limit on how many you pair. It needs the POS add-on, the same one that lets a machine sell. POS and the counter in the docs covers what the add-on includes.