The board is the following:
http://www.ebay.com/itm/USB-4-Channel-Relay-Board-RS232-Serial-controlled-/280879280954
As I said, it's an independent board with its own microcontroller. I would assume they integrate diodes on the PCB, it would be stupid not to. But who knows hm? The inductive load is a small motor, 1.55 amps, 120VAC.