IANAL so please don’t take my word for it. But if I understood it correctly, this is indeed legal. You don’t have to offer your stuff for free. And as long as you let the user decide if they want to pay with money or with data, it’s legal. The important part is, that the user needs to give consent, which is the case here. Not talking about the morality of it though.

You mean Wind🤮ws?

They dropped the Tidal integration and I’m still heartbroken. It was the best setup for music discovery. Haven’t found a replacement yet.