Hello Indrini,
Hope you're having a great day! It's absolutely fine to use our music packs in projects other than games. The Music assets are catered towards Game Development, however there are no restrictions as to where you may use them. So yeah, using them as the Background Music in your YouTube videos is not at all restricted.
Redistribution of the music files is not permitted though, you may go through the included license for more details.
Have a great time with your YouTube endeavor, glad we could be of help!!