I hesitate to get involved with this thread; however, I addressed some of the weaknesses in this apparent diversity of re-use graph by truncating the time-line to relevant / recent memory; ie. since 2010 - a while ago. That rather changes the picture. So for an alternative (now also out-of-date) graph see: http://people.gnome.org/~michael/blog/2011-11-18-graphs.html