I am thinking of doing a web app that uses keywords to query Spotify web API for public user playlists, and then do an online mashup with my own music retrieval system. Is it allowed? Can the playlist names and tracks be cached for the purpose of categorization.
I read through the Terms of Use and saw this: "Do not improperly access, alter or store the Spotify Service or Spotify Content, including (i) using any robot, spider, site search/retrieval application, or other tool to retrieve, duplicate, or index any portion of the Spotify Service or Spotify Content (which includes playlist data) or collect information about Spotify users for any unauthorized purpose;"
Paul Lamere does something similar with Playlist Miner: https://github.com/plamere/playlistminer. But he is an EchoNest employee.