From Delta's international Contract of Carriage, rule 116:
I. Governing Rules for Codeshare Flights
For codeshare services, each customer will be entitled to the free baggage allowance and charged the excess baggage charges (when applicable) of the Marketing Carrier, regardless of who the Operating Carrier is. If the need arises for operational or safety related reasons, the Operating Carrier may require that carry-on baggage be checked at the gate, but no additional excess baggage charges will apply.