If I remember correctly, GOLD team did said something about there must be an upkeep fee for GOLD holders but why keeping GOLD on an exchange don't invoke this fee tho? So how the exchange would pay for our GOLD upkeep?
I'd say that it's probably some sort of bonus to attract exchanges into listing GOLD. And this would mean that GOLD team would pay the storage fess for the involved GOLD from their pockets / revenues.