When the copyright lapsed in 1974, television stations worldwide began looping the movie into their schedules. It was free programming, a cash gusher with no royalties paid to its creators, and the widespread exposure informed the imagination of generations of families huddled around the television over the holidays.
I guess the copyright issue was not totally left to the open. Here's something else I just saw:
Republic Pictures heard just about enough of America singing Auld Lang Syne and weeping every year without anyone getting a cut of it and enforced its claim on the film's copyright in 1993. That copyright went to Paramount and after sprawling parent company Viacom bought Republic in 1998. Since the copyright clampdown, former GE holding and recent Comcast subsidiary NBC has held the broadcast license on the film and been particularly stingy about it. It's A Wonderful Life now airs only twice a year: Once on Christmas Eve and, this year, on Saturday, Dec. 3.