I'm not sure I understand correctly. (The term Authorized User has a specific meaning at American Express, which is different from the way it is used by other card issuers.) If someone else is the basic cardholder on the Business Gold account, and if you hold a supplementary card on that same account, you should be able to link your frequent flyer accounts to his/her Membership Rewards account with the possible exception of Emirates. You need to link the accounts before you can transfer, have you tried to link?