Today, people want access to their applications on their PCs at work, on their tablets in meetings and on their smart-phones on the move. As such your product and all its features need to be supported on a majority, if not all, devices and browsers.
Charting for you is a part of your product spectrum, an important part of it, but definitely not the entire spectrum. It is a means to an end and hence rapid developer adoption, agile implementation and quick results is what you need from the component you choose.
For application in commercial website and project, please purchase a commercial license.
If you are building an application, data visualization might not be your core strength. So when you face a problem, you might need some external support to solve it. Support can come in many forms like personal, forum or community sites like StackOverflow. If you are on a tight schedule you would not want to wait for an answer on StackOverflow. Personal support or dedicated forum would be very useful in this case. Therefor it is very important to find a vendor who provides personalized technical support as well, typically with a guaranteed turnaround time.