As the PP said - anybody. It doesn't matter who you booked through, how you booked, how much you paid, if you have a package, or even what phase the moon was in when you booked. Its free if you are staying at a Disney owned resort.
Let me add to these posts....both of which are 100% correct. You must have an existing DME reservation before you arrive at MCO. Just call whomever you made your resort reservation with and add the DME reservation. That way you will get the DME packet with vouchers and luggage tags in it prior to travel and you'll have no issues when you arrive at the DME area.