Add the Internet Archive to the sources available for movies
There are already thousands of movies and TV shows that are out of copyright available via https://archive.org/details/movies and more arriving all the time. They should be linked alongside the JustWatch data where available.
This would really be added to JustWatch as a watch now source. Otherwise, do they have a public API to get the streaming info?
David Russell Brake commented
I don't know enough about APIs to give details but there's a bunch of data here https://archive.org/services/docs/api/ and basically all of their stuff is browsable, accessible and almost never "leaves"- it only gets added to.