I'm working on a proprietary application and am considering using QtCharts, a GPL licensed low-level plotting library. The plotting aspect is not the IP we are trying to protect so I'm trying to think if there is a fair way to have my cake and eat it too.
I'm considering the following
- Keep all our IP in proprietary libraries
- Change the main application to a GPL compatible license
- Have the main application load both our IP libraries and QtCharts
I know this isn't as open as FSF would like, but it is more than just a GPL condom. Someone could take the main application's source code and reasonably insert their own libraries to do something useful and more than just directly using QtCharts themselves.
Is this legal? As authors of both the main application and the IP libraries I'm hoping we can grant ourselves the necessary exceptions (link). Does the answer change if the IP libraries depend on other libraries not written by us but with permissive licenses?
Is this fair?
** UPDATE **
I think I understand Phillip Kendall's point better now. Even if the main application is changed to a GPL license, use of QtCharts would prevent us from issuing the exception to use the proprietary library.
So the next logical step, for me it,
- Move IP to separate application (no GPL dependencies)
- Create an IPC library to talk to the proprietary application. This would be released under GPL with some sort of exception to use in the proprietary application.
- Change the GPL main application, using QtCharts, to use this IPC library.
This feels more like it is violating the intent of the GPL but legally is it on stronger footing?