Here is my propose, migrate from SVG::Graph to Highcharts Javascript based graphing solution.
It can be used as GPL, as VisageApp (http://auxesis.github.com/visage/#about) already got GPL license for it.
The main advantages we will have using it instead of the actual one is that we can create zoomable graphs, which could help, for example, display correctly "Commits by Authors" (https://www.chiliproject.org/projects/chiliproject/repository/statistics).
Despite the fact of zoomable graphs, we could also benefits from animations and interactivity, to display context information "on mouse over" for example.
Also their graphs are more visual appealing than what we have today.
Another option is to work with g.Raphaël (https://github.com/DmitryBaranovskiy/g.raphael), it's based on Raphaël Javascript library. The project is actively being developed, and as it uses Raphaël, it just fit well with this feature request: https://www.chiliproject.org/issues/782 as it's based on Raphaël too.
And finally Flot, http://code.google.com/p/flot/ that have some of the functionality of Highcharts, but a bitty ugly.