I have made a bit of headway. But you and @matthias will probably not like it, because I decided to go with Python + API. I added a few functions to the small library we maintain. Result:
I have since made some tweaks to the visualization and saved two Gource configuration files for two different situations. Also, the output from Gource is higher resolution than what I saved on YouTube. But still, not sure how meaningful this is a data visualization 