No, Delta is a free app for both iOS and Android! You can continue to use the app for free as well.
We do, however, offer a Delta PRO subscription. Delta PRO is a monthly/yearly subscription that packages extra empowering features on top of what Delta already offers. More details about Delta PRO and what it offers can be found here.
PRO TIP: If you are looking to find out how much Delta PRO costs, you can learn more about this here.