Canorus is the next generation music score editor. It is the official successor of NoteEdit. It uses Qt4, has scripting capibilities and uses modern development standards like eclipse, patterns and test units as base.
Clips is a Java based music composing tool separating chords and rythms: Create a funky rythm and turn it into a song by varying the chords. Just for the hell of it, it is also specially designed to be portable to mobile platforms (e.g. Android).