Public domain movies, like public-domain books, have gone out of copyright and you are free to use them. I love old books and old movies so I have been recently adding to my collection. Here is how you get movies from the internet onto iTunes.
The format that you need for an iTunes video is MP4. There are many sites on the web that have public-domain movies. Lately, I've been at this one http://imovies.blogspot.com. Hopefully, this link will still be working at the time you read this post, but if not, well, just Google "public domain movies with mp4".
|Be sure that MP4 is an option|
|Add to Library in iTunes|
I just downloaded "The Road to Bali". I'm a big fan of Bob Hope and Dorothy LaMour, so I'm watching it right now.