Radio channels

No, there is no agreement between Sonos and any radio stations, nor is there any money trading hands. Think of Sonos products much like a TV set. You can tune to many different channels, but the TV manufacturer only provides the ability to tune to the channels, and has no control over what is on those channels. Sonos provides the ability to tune to many different ‘channels as well, just for radio. For instance, they can use TuneIn, iHeart Radio, myRadio, and several other ‘channels’ that provide radio service, but they don’t pay any of them for that, and the various streaming services don’t pay Sonos either, it is just a method for the streaming service to reach an additional audience. 
 

Many of these various streaming services make money by inserting their own advertising as a ‘pre-roll’ before starting the stream. Sonos doesn’t have any control over that, nor do they receive any portion of that money. However, frequently these radio streamers has exclusivity agreement in place, so if the radio station choose to be associated with streamer X, they are not allowed to be streamed by streamer Y as well.

You can add a direct stream, such as you mentioned, directly to your Sonos by following the instructions in the setting up an internet radio station FAQ.