Thanks for your kind comment, and for sharing this interesting article!
I just want to make it clear that using Openwhyd as a back-end for your app will allow it to play only tracks from the streaming platforms that we support. (e.g. YouTube, Soundcloud, etc…)
It means that, if your app relies solely on openwhyd.org’s back-end to store playlists, it may not be possible to include tracks that are on Spotify but not on the public/free streaming sites that Openwhyd supports. Except if you host the corresponding audio files online, with a publicly-accessible URL.
Feel free to contact me by email at contact @ openwhyd.org to tell me more about your project!