Surprised it hasn't been mentioned yet but WizNote is a pretty decent Evernote clone with clients for all platforms. Use Google translate on the site: https://wiz.cn/
Though I also recommend this book, their example code teaches bad habits (such as assignment within conditionals and horrendous compound statements) which should be avoided in any sort of production code.
Spotify is 100% licensed. AFAIK, Grooveshark is more like Napster in that it's a free-for-all with user uploaded content, though they have worked out deals with some of the record companies.
Does the app produce a unique coded signal of flashing screen colours for each user? Otherwise, what's to stop someone from loading an image of their own face with someone else's barcode onto their smartphone and stealing sandwiches?