[Paraview] GPL and Paraview and Qt

[Hendrik Belitz]

Hi Bonnie,

although I'm no lawyer, I had to deal with a similar problem some years ago. Don't take this too seriously, this is only my point of view based on my experience with similar issues. I definitely suggest to ask some GPL guru on this for a final statement.

Anne it absolutely right in stating that you have to publish your code under a GPL license when using the open source license of Qt. But be also aware of the fact that you only need to share the source code when distributing your binaries. Since you're developing an in-house project, you're not sharing your binary versions, which in turn means that you don't have to publish your source code in the open.

> It is whether or not we would post the source to our changes back to the open source community.

In fact, this is not what the GPL states. It only states that you have to distribute your source code along with your binary version. 

> Can someone please clarify theimplications of GPL?  If I extend Paraview to invoke our commercial applications via a custom .dll, I could make Paraview extensions available, butI wouldn’t make the custom .dll available.  Is this complying withGPL?  We wouldn’t be reselling the SW – only using it in-house.

This is not complying with the GPL.  As soon as you make paraview dependent on your in-house modules, you need to share these. The only way to prevent this is to implement loose coupling, e.g. making a GPLed plugin interface for paraview which you could use in-house for your own plugins that you won't distribute. Using dynamic linking is not enough.

> We will be adding enhancements to itkSnapand Paraview at least, if not vtk and itk.  And we would be able to postthose to the open source community as long as we can have some custom .dllswhich we don’t share.

I cannot see what this has to do with the actual problem. Are those additions to itkSNAP and Paraview equivalent to your own in-house modules? Are these used by your in-house modules?

> Do I understand this correctly?  Ifwe did want to sell an app that depends on vtk .dlls, other than keeping thecopy left in place, am I free to do this?

Yes, VTK, like ITK, is licensed under a BSD-Style license which does not restrict any commercial and/or close-source distribution of your application.


Regards,
 Hendrik