It's complicated. The copyright on the film itself lapsed in 1974, but the copyright on the original story "The Greatest Gift" and the copyright on the original score have not lapsed. Republic Pictures (now owned by Paramount) controls the rights to the film as a derivative work of "The Greatest...
My copy from Barnes & Noble finally arrived today. These digibooks for Sony's Capra pictures are really something special. I wish Sony had the rights to It's a Wonderful Life.
FYI, Barnes & Noble's website currently has it for $13.35, also with the November 22nd release date. Worth it if you're a member and get free express shipping.