RGraph is a HTML5 canvas graph library. It uses features that became available in HTML5 (specifically, the CANVAS tag) to produce a wide variety of graph types: bar chart, bi-polar chart (also known as an age frequency chart), donut chart, funnel chart, gantt chart, horizontal bar chart, LED display, line graph, meter, odometer, pie chart, progress bar, rose chart, scatter graph and traditional radar chart. RGraph is covered by the RGraph License.
RGraph is covered by the RGraph license. A summary is that for commercial/business use there is a small one-time licensing fee to pay. For non-commercial purposes it's freely usable. There are some licensing FAQs that should help to answer any questions you might have. If you need one, you can get an invoice here.
If you have any questions about RGraph licensing, you can send your question to: licensing@rgraph.net. If your question is of a support nature though, please use the support forum.