Royalty free doesn't mean you can use it any way you like. You need to read the fine print. If something is being used for promotion, which means you hope to gain financially from it, the "royalty free" license may change for you. Sometimes people require credit, sometimes they stipulate that you can't use it for that purpose. You need to read the fine print! Yes, I'm going to say that a lot.
After 8 years of creating book trailers and over 600 book trailers created, I've seen a lot of issues come up regarding book trailers and distribution. I've seen a book video producer get sued and I've seen big-name authors have to remove their videos because of copyright issues. Luckily, I have never had that happen to me. Why? Because I read the fine print. And because I keep copies of the licenses of EVERYTHING I use in any book trailer.
Last month we had a problem with a video being taken down from YouTube. Time Warner Entertainment said we had infringed on their copyright. YouTube threatened to remove our entire profile. We have over 600 videos on that profile. Here's the great thing about always taking care to keep licenses on hand, I did not have to panic. I was frustrated, but not panicked. And within 24 hours I was able to have the video put back up. Time Warner Entertainment had made a mistake and one phone call to their attorney fixed the problem. And guess what? They were apologetic and nice. It was truly that easy to fix.
Anyone creating book video and distributing that video online is on the cutting edge of a new marketing opportunity. Like anyone else who blazes trails, you also get to be the first to make mistakes and the first to encounter problems that you then get to solve. Once you solve it, it is solved for everyone that comes after you, even those who will be competitors and who will knock your company name while they benefit from your hard work. That's the breaks.
There are things you can do while blazing that trail that can help you stay out of trouble. Yeah, I'm gonna say it...Read the Fine Print!