Hi David and everybody,
I often think we teachers go about things in the wrong way. We bat about on the Internet and come across an article or video and think : "Oh, that would be just right for my XXXX class."
What we should be doing is thinking : "I need an article on YYYY for my XXXX class." and then doing a search for YYYY with "Public domain", "Creative commons", "open access" or "PLOS" tacked on the end. There are even search engines specialised in this.
Another thing is not to bother with the big guys - they usually won't even take the time to reply, but the little guys and gals will and be flattered you asked for permission to use their work.
We could even hand over the research for content to students: sure they'll come up with some dicey stuff but isn't that our job too? To help them learn to recognise the dicey stuff. They won't learn that if they're just spoon fed the good stuff.
I'm not sure I'm convinced, but the ideas of Richard Stallman about copyleft certainly make interesting reading.