Just from a cursory glance, it appears that Chartjs is entirely free and you can do what you want with it, while Highcharts is not.

It would be nice if this distinction was stated unambiguously on the front page

here's the license if you were looking for it like I was

https://github.com/nnnick/Chart.js/blob/master/LICENSE.md

Took me ages to find the license, I ended up clicking documentation and still having to search for the word license to find it. I wish it was more prominent on the landing page.

Highcharts is free for non commercial

Big fan of Highcharts. Like that you can export charts to a png. Big deal for me, don't think chart.js offers anything like that?

FusionCharts can export charts to PNG, JPG, PDF and SVG. I've been trying both FusionCharts and HighCharts for past few weeks and I can say that I am a bit inclined towards FusionCharts. Had this discussion the other day as well when Epoch[1] was released.

[1] https://news.ycombinator.com/item?id=7948560

Yep, you can call .toBase64Image() on your chart instance to return a png image encoded as a base 64 data url.

I really like the feel of HighCharts. I've been using HighStock (their financial charts) for traffic analytics graphs and it works really well.