Billboard 2.0.0 has just been released:

http://thp.io/2012/billboard/

This is the open source release of Billboard under the GNU GPLv3 or later, the Git repository is here:

https://github.com/thp/billboard

The source tarball can be found on the Billboard website.

Apart from the usual translation updates, this also adds a new feature:

Volume monitoring ({volume}, {volume-bar} and {song-volume-bar})