Document what can be done with GPL v3 vs commercial license

[brodycj]

I think this needs to be clarified. The free GPL v3 license allows for internal development, testing, and distribution within an organization (http://www.gnu.org/licenses/gpl-faq.html#InternalDistribution). This would be consistent with the Apple Developer Enterprise program (https://developer.apple.com/programs/enterprise/).

A commercial license would be required to distribute an app to another party without making the source code available.

GPL v3 does include a system library exception, which covers linking to closed-source system libraries. There are some more details and fine points in the following:

• http://www.gnu.org/licenses/quick-guide-gplv3.html
• http://www.gnu.org/licenses/gpl-3.0.html
• https://opensource.stackexchange.com/questions/2203/why-is-the-definition-of-system-libraries-in-gplv3-phrased-the-way-it-is