According to Wikipedia, a royalty free license grants you the right to use copyrighted material (music in our case) without the need to pay royalties or license fees for each use or per volume sold, or certain time period of use or sales.
All our licenses grant you the right to use our music indefinitely and in as many projects as you like without the need to purchase additional licenses. That’s what we mean by “royalty free”.
Royalty free license simplifies music licensing by removing the need to negotiate licensing fees with the Performance Rights Organizations (as the name implies, there are no performance royalties to collect) and gives you the right to use copyrighted music without the need to pay royalties for recurring use (that is, for each time the music is “publicly performed” to the listener).
Many composers offer their music with royalty free license, either directly or through royalty free marketplaces.