Geoff said:
Last time I looked, in the U.S., copyright protection lasts for the
life of the author plus 50 years. I don't know what happens when the
"author" is a corporate entity. With "renewals" the term could last
indefinitely.
You haven't looked recently. In 1998, copyright terms in the U.S. were
extended to life of the author plus 70 years. For corporate entities
it's now 95 years after publication or 120 years after creation,
whichever comes first. No renewal is required.
Along with the sheer amount of time works are protected, the would-be
licenser must determine whether authors are still alive and if not
when they died and who their literary executors are. Again, trivial if
it's Disney and probably easy if it's Al Jolson, but if you just want to
make a legal copy of a borrowed book from a little-known author who
was last in print in the 1920s, it's extremely difficult to determine.
Most individuals would just make an illegal copy, but a library seeking
to scan a brittle book and put it on the web for the greater convenience
of its users can't do it. Maybe Google Books will end up making case
law that overturns it, but most libraries are a lot more conservative
legally than Google Books.
-- Patrick