Having read this post : Privacy risk in using Google APIs, I am wondering what are the alternatives with no privacy concern, esp. for website charting development(e.g. chart.js)?
I've used RGraph to make custom charts. I consider RGraph an undervalued tool, with tons of options and details. By default is not very nice, but if you just mimic the Google Chart colors and tinker a bit, your graphs become "cute and good enough". Also, lots of demos, examples and good documentation.