You can check out the PowerPlot library which is an iOS native library. It is the only choice (to my knowledge) that not only has the "usual" assortment of charts, but also graphs (with nodes and connections) among the views. It is not based on OpenGL, but on Quartz. It also does not target the desktop version of MacOS, focusing specifically on iOS.
Licensing policy is dual license - developers can choose GPLv3 or a commercial one.
