It draws on inspiration from Plotr and PlotKit, and several other commercial packages. But also from venerable old gnuplot - there's nothing more boring than hand-picking axis scales so I wanted the default algorithm to be smart.
The project actually got started because we were growing dissatisfied with Plotr which looks nice but is pretty dumb when it comes to auto-detecting stuff and didn't have any interactive features which we needed for a custom web-based business intelligence application.
I find it interesting that I initially thought plotting to be a hard problem - but this project got started a couple of months ago and I've only been hacking on it sporadically. Right now, the library is still missing support for time series, but is otherwise pretty much feature-complete for what we need it to do. I'm looking forward to hearing other people's opinion.