Zong! is an open-source music notation software, which is currently under development. It will be available on a number of devices and systems, including Windows, Mac OS X, Linux, Android and the Web (HTML5 + JS).
On this website, started in September 2013, we will provide information about the project and present news in the blog. We will provide access to the Java source repository and to early builds. At this moment, it is only interesting for developers. If you are looking for an existing free music notation program, have a look at MuseScore.