Superman first appeared in Action Comics #1 in 1938. The character will enter the public domain in 2033. "Anyone can use what's in the public domain without getting permission or compensating the owner," says The Week, but that doesn't mean you can use the latest version of the superhero in your own comic book or movie.
As reported in The Week:
Just because a character enters the public domain "doesn't mean anyone can use the character however they wish," Michael Grothaus explained in Fast Company. "U.S. copyright law is complex, and public domain comes with caveats." There are limits to what you can do to public domain characters.
First, new projects can only use public domain characters as they existed 95 years ago. For example, when Superman enters the public domain in 2033, new character variations must be based on how he appeared in DC Comics' "Action Comics #1" in 1938. That version of Superman didn't fly, and his costume was very different from the iconic suit the superhero is currently known for. If someone made a Superman movie in 2033 in which he could fly, Warner Bros. would have a case for copyright infringement "since DC gifted Superman with flight power later in the character's mythology and it would still own the copyright over that version of Superman," Grothaus added.
