See Section 2C of
Apple's Software License Agreement for iLife. You are free to broadcast and distribute them as part of an original soundtrack - you'll be fine as long as you're not trying to resell the sound effects or music on their own.
My reading of 2C is if you use Apple's sound clips, you're fine. If you use their products to create your own original music, that's fine. (They aren't claiming ownership.) If you use someone else's accessed through their service, you still need to get the permissions. So if you create music and use the twitting birds clip, that's cool. If you use a jazz clip that comes with the software, that's cool. Those were hired services for Apple so they own the rights which they allow you to use royalty free.
Refer to Section 2G.
"... Title and intellectual property rights in and to any content displayed by or access through the Apple Software belongs to the respective content owner. .... You man not use, extract or distribute, commercially or otherwise, on a standalone basis ... outside of the context of intended use as part of the Apple Software."
Purchasing anything from such a site, you are buying personal performance rights. Be careful about including materials downloaded from music sites. In general, if it's been created in the last 75 years and you haven't personally created it or hired its creation, you will need to pay for the public performance rights.
This is not legal advice. I am not a lawyer. But it is easier to pay the royalty up front, than the legal fees down the road. Plus even if you concede and agree to pull it out of your movie, now you have wasted a lot of time and production effort. Better to find something royalty free or find someone who will do the music.
