It is my understanding all the films offered in The Prelinger Archives are in the public domain. There is some amazing material on that website. Use the search box and travel back in time. Try old time radio.
You will find this notice on home page, by truncating the URL in my first post.
You are warmly encouraged to download, use and reproduce these films in whole or in part, in any medium or market throughout the world. You are also warmly encouraged to share, exchange, redistribute, transfer and copy these films, and especially encouraged to do so for free.
Some gems buried in there, and it is fun to look for them.