This statement on the OC200 voucher creation page reads differently to my understanding. I've asked this question here and TP link tod medifferently. 

But from what this reads it seem that the code can be used by another device/s but not at the same time, please correct me  if I'm understanding it wrong.

Because my worry is that if the code is sheared, then others can use the network when the code wasn't issued to them.