From: Dan Whaley <[log in to unmask]>
Date: Tue, Aug 6, 2019 at 10:12 AM

https://www.vice.com/en_us/article/kz4e3e/millions-of-books-are-secretly-in-the-public-domain-you-can-download-them-free

"Prior to 1964, books had a 28-year copyright term. Extending it required
authors or publishers to send in a separate form, and lots of people didn’t
end up doing that. Thanks to the efforts of the New York Public Library,
many of those public domain books are now free online. Through the 1970s,
the Library of Congress published the Catalog of Copyright Entries, all the
registration and renewals of America’s books. The Internet Archive has
digital copies of these, but computers couldn't read all the information
and figuring out which books were public domain, and thus could be uploaded
legally, was tedious. The actual, extremely convoluted specifics of why
these books are in the public domain are detailed in a post by the New York
Public Library, which recently paid to parse the information in the Catalog
of Copyright Entries.

In a massive undertaking, the NYPL converted the registration and copyright
information into an XML format. Now, the old copyrights are searchable and
we know when, and if, they were renewed. Around 80 percent of all the books
published from 1923 to 1964 are in the public domain, and lots of people
had no idea until now."