I can't verify it right now but out of curiosity a while back I had a look and I'm sure Spotify were streaming their audio through websockets in some way - or a

I can't verify it right now but out of curiosity a while back I had a look and I'm sure Spotify were streaming their audio through websockets in some way - or at least linking to audio chunks in the websocket. You'd definitely have to download, remux, rehost the audio for it to work with podcast clients