Once iTunes Radio is a part of Apple Music, you will have to subscribe to the latter to use it. Apple Music is $9.99 a month for individuals, or $14.99 monthly for a family with up to six people. Apple's iTunes Radio is only available in the U.S. and Australia. According to the Financial Times, in just six months Apple has signed up 10 million subscribers for Apple Music. Already, that is half the number of subscribers paying every month to use industry leader Spotify.
This doesn't mean that Apple doesn't have a free radio station for iOS users. Beats 1, Apple's 24/7 radio station, is free to listen to via the Apple Music app on iOS and Android. The station features popular DJs like Zane Lowe in Los Angeles, Ebro Darden in New York, and Julie Adenuga in London. Starting on January 28th, all of Apple's radio stations outside of Beats 1 will only be available to Apple Music subscribers.