Here's the link to the github source code for the Milestone Burnup Chart.
GitHub - KilobytesandBits/MilestoneBurnupChart: Milestone Burnup Chart for Rally
I followed the link expecting to find the usual hundreds of lines of HTML that I could inspect and adapt. Instead there is a very short shell that doesn't seem to do much itself, and doesn't point me clearly to the place where the real code is.
So I guess I need to know where the real code is.