“This means that you can now copy, distribute, and use the contents of these books without any restrictions (certain limitations may still apply in some jurisdictions).”
Shuzo Fujimoto’s self-published origami books are nearly impossible to find in print. His children put all five into the public domain, and Michał Kosmulski had them professionally scanned. Copyright would have locked them up for decades more. His heirs gave them away so people could keep folding.