Can't speak for Planetside, but I doubt Planetside cares much about the route of the financial transaction. In the end, it is probably very typical for commercial customers, that the procurement department orders licenses for the creative department, for example, in which case the person putting in the order is not the end user of the product.
I guess it's safe to assume that the true meaning of this message is, that only one person is licensed to use this key, and that you are not to distribute the key to anyone else.
It would not be ok if both you and your brother are using this key.
That's how I would interprete it. You will have to wait for the explanation by a Planetside offical though, to be safe.
Frank
