We want to hook up free charts to our backend service and feed the data into charts ourselves ... we have our own format . So basically we are looking for javascript / HTML5 code without service or data integrated but very rich as in bitfinex, BitMex and with free license , so we could put it on our website , it does not matter if we have to display license as long as it's free. I will look into tradeview as it's the most suggested by all users here.
If you have the data in JSON format then there are many online libraries which can generate a chart for you in different formats.
Infact you can even play with google charts.