When I went to the D23 Expo in 2009 there were no physical tickets. At registration name was checked off a list, a lanyard with credentials given, and a wristband attached (for actual D23 members).
At the last Expo I was not a D23 member, and I purchased a ticket on-line. Non-members can still purchase tickets for this Expo as well. As a D23 member you can purchase tickets for a non-member guest. My guess is that you could transfer your tickets to someone else. I am not sure of D23 policies regarding selling tickets.