The pChart library is released under two different licenses. If your application is not a commercial one (eg: you make no money by redistributing it) then the GNU GPLv3 license (General Public License) applies. This license allows you to freely integrate this library in your applications, modify the code and redistribute it in bundled packages as long as your application is also distributed with the GPL license.
If your application can't meet the GPL license or is a commercial one (eg: the library is integrated in a software or an appliance you're selling) then you'll have to buy a commercial license. With this license you don't need to make publicly available your application code under the GPL license terms. Commercial license price are depending of your needs :
Government R&D license
This license is dedicated for governmental institutions that are working in the research and development areas of science. (Physics, Biological, ...) It allows the owners to freely use pChart on any number of intranets or publicly accessibles internet web sites. Commercial redistributed applications bundled with pChart are also permited.