From Delta.com

"Can I transfer ownership of an eCredit?

Yes. To transfer an eCredit to someone else, you'll need to give them the original 13 digit voucher number and complete name as it is printed on the voucher receipt. Paper vouchers must be transferred in person at a Delta ticket counter or Ticket Office Location."

http://www.delta.com/help/faqs/your_...ries/index.jsp