> Blender’s scripting API is an integral part of the software. Blender add-ons work, look and feel like Blender features. And as for any other Blender feature that means – it has to be free, free and free forever! Paying for an add-on can only mean access to the add-on download service… offering it to you as GNU GPL. Your freedom as a user and developer is guaranteed.
This is the same issue that wordpress has faced in the past, I believe - are proprietary plugins allowed to a GPLed product?
Notice that the Blender Game Engine is discontinued anyway. People seem to instead use Armory3D[1], which has full Blender integration and is zlib licensed[2].
I reckon a fair way is if blender has a proprietary licence available to plugin vendors who wants to sell non-GPL version of their plugin. I suppose the proprietary licence can be a small share of the profit from the plugin sales.
This is the same issue that wordpress has faced in the past, I believe - are proprietary plugins allowed to a GPLed product?