Yes, radio.de is free for you! We are an ad-supported service and do not charge you for listening to stations via radio.de. Please note that you need a stable internet connection to use radio.de and that your network provider may charge you if you do not have an internet flat rate. Therefore, end the playback with the pause button if you do not want to listen anymore.
Perhaps a direct listening experience would be worth a subscription to you? We offer radio.de PRIME as a subscription for the app.