Your Questions:
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Not yet, but we plan to release a score viewer component for your Java desktop application, Android app and even for web pages (HTML5/JS). This component will be able to display and playback scores. It will be released under the GPL license, which allows free usage in your program, as long as it is free software, too. If you have a commercial application, we can arrange a special license for you. Please contact us. (Andi, 2013-10-24)
When will Zong! be available for download or for usage within my own software project?
Currently there is no long-term time plan for Zong!, because it is currently developed within our spare time, which depends on other projects. But expect to see a first public beta version in late 2015. You can also follow our current project planning and try out the latest development versions available on github. (Andi, 2015-01-25)