CherryMusic is completely free, you can get the source code from github and modify it to your will. It's released under a GPL license.
After downloading CherryMusic, you must merely tell it where to look for your music. That's all. CherryMusic takes care of all the database bullshit and so on.
You can listen to your music on all HTML5 compliant devices, that includes your pretty smart phone (Android or iPhone) as well as just about any modern browser.
You can create accounts for your friends and share playlists. Just like ol'times, give away a cassette tape.
CherryMusic has a built-in database, that will index your music. Find your favorite song in an instant!
CherryMusic can automatically fetch the album cover art for all your music. But don't worry, we don't change anything in your collection.
CherryMusic is a standalone music server written in Python and based on CherryPy and jPlayer. It is intended to be an alternative to Last.fm, Spotify, Grooveshark... you name it.