Fair use is one of those US legal concepts that, like the first amendment guarantee of freedom of speech, gets badly misused on the internet. Chances are you don’t understand it. That’s okay; I don’t fully understand it, either. But there are some misconceptions that you absolutely positively should rip out of your brain.
The most common and most pernicious one is that, if you only use a little bit of a song or excerpt a tiny piece of a novel, that’s fair use. Well, no. That can be a part of a fair use defense, but there’s more to it than that. Saying “I only used a bit, so it’s fair use!” is like going up to a cow in a field and saying, “Look! I made a hamburger!”
There are four things that go into fair use. Yes, length is one of them. If you use a short excerpt compared to the entire length of the work, you’ll more easily be able to claim fair use. But there are three other things you need to be doing for you to claim fair use.
What are you using the excerpt for? You need to do something transformative with it. You also need to use it to comment on or expand upon the original work. Using it for criticism about the actual work? Excellent. Using it because it would sound cool in your movie? Not so good.
What’s the nature of the work? Are you excerpting facts? Or are you taking pieces from a work of fiction?
Finally, what’s your excerpt going to do to the copyright holder’s ability to sell the original work? If you’re using the excerpt in something that will compete with the original for market share, you can’t easily claim fair use.
Those four elements are only guidelines, though. Take the restriction on length. Copying an entire TV show to watch it later? Fair use. Using just over one minute of a 72-minute Charlie Chaplin film in a new report of Chaplain’s death? Not fair use. About the only way to really know if something is fair use or not is to fight it out in court, at which point you might as well turn large piles of cash into bonfires.
Now I will sit back and wait for my lawyer friends to correct this post, because Aahz’s law doesn’t just apply to Usenet.
(And in case that last sentence doesn’t tip you off: I am not a lawyer, and this does not count as true legal advice. Consult your lawyer if fair use lasts for longer than four hours.)