rorschach
macrumors 68020
Spotify allows downloading. Not downloading into your iTunes library, of course, but downloading into the Spotify app for offline playback.
But you cannot access those files downloaded through Spotify; at least not through any legitimate/officially supported way. They are purely for use within the app to support offline playback. Not so with an app that downloads rips an MP3 from YouTube, etc., for free and lets you do whatever you want with it.
Spotify also has license agreements to do what they do. Does "iDownloader Pro Free"?