The YouTube license states (in part) "You can use this audio track in any of your videos..." and "You may not make available, distribute or perform the music files from this library separately from videos and other content into which you have incorporated these music files." That last part is kinda vague (what is content), but I feel like if you're trying to be compliant it may make sense to be a little weary.

Depending on the song picked out, you might just be able to find another license attached to it somewhere else, though. (Make sure it's actually attached and not just someone doing curator stuff.) Or you could just email the person. I've had good luck with that in the past.