Quick Review, a copyright lasts for the Life of the Creator + 50 years, which was extended by the Sunny bono copyright extension act to 70 years.
So a work made by someone who died 70 years ago, 2011-70 = 1941 has a chance of going to public domain...
Conan is an example of matter where he can be considered public domain but there is long ongoing litigation that he's not because of the writers who made more stories about conan well after Howards death.
The practice is similar to when Xerox patented every little innovation in the Photocopier tech so that no one could ever compete, it was called a patent thicket and was considered an abuse of the patent law.
I'm not sure of the merits of allowing for these Copyright thickets encouraging copyright owners to continue to enjoy the franchise well past the conventional limit.
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