Tarmack
Rhetorical Porcupine
Of course they can strike you if you use Royalty Free music. Royalty free doesn't mean free. It means you pay once, not an ongoing royalty for use. If you didn't pay once, then you don't have the proper license and are engaging in copyright infringment. If you do pay for the music, make sure the license specifically allows online monetization, not all of them allow YouTube monetization. A place like Audiomicro is good for this because the standard license actually mentions YouTube itself as an allowed location. I have licensed my intro track from them and I think it cost me around $40.
For truely free music, you need to search for Creative Commons. This license has some variables but basically it usually boils down to a blanket permission the artist gives to anyone that the music can be used for whatever you want for free, as long as you credit the artist every time it's used. So if you find a song to use for an intro, you must put the title, artist and a linkback to their site in the description of every video using that song.
For truely free music, you need to search for Creative Commons. This license has some variables but basically it usually boils down to a blanket permission the artist gives to anyone that the music can be used for whatever you want for free, as long as you credit the artist every time it's used. So if you find a song to use for an intro, you must put the title, artist and a linkback to their site in the description of every video using that song.