The Specs of the cord should be printed on the cable itself. I would bet the cable has 300 or even 600v insulation so 240v would be fine. The gauge of the conductors would determine current, I would guess they could handle 20A.
The OpenEVSE 30A kits can charge at 120 and 240. The 50A kit is limited to 240 only.
I wonder if the LEAF supplied cord with their 110V "charger" could be used with this 220V system? would the cord handle the amperage of 30A? it would also be a leap of faith when I cut it off since that is the only cord I have. can this system be set up to also charge at 110V, maybe using a plug adapter?