Never mind.
Based on the T & C, it is not possible unless the seller is willing to buy the tickets on his credit card. It is possible if both parties know each other.
Reservations & Ticketing: Valid for new ticket purchases through alaskaair.com, Alaska Airlines Reservations, or Horizon Air Reservations. The Companion Ticket Discount Code is redeemed at time of ticketing and is void for future changes or purchases. Traveler and/or Purchaser name must match the name issued on the Discount Code. Credit card required for purchase.