We were discussing this at length in last year’s GSoC in one of the sessions. Probably one of those were Google shows-off new technology and many developers including me said that Highcharts doesn’t have an real-FOSS alternative. Many libraries based on D3 (MetricsGraphics, NVD3, C3, n3-charts, Rickshaw) are trying to be it, but I agree with @burke that they aren’t as good as Highcharts yet, but they are rapidly improving. We probably need to give those charting libraries a little more time for maturity…