Actually it depends if the company ships nukes as a product or not.
When a company write a custom modules :
1/ they have full copyright on it and can license it whatever they want
2/ if they distribute the component with Nukes, I think it must be licensed under GPL
I had the same questions awhile back and Julien did a pretty good job explaining as much as he understands. I'm still not sure that i understand, but enough for what i need to know. see the previous post here...
I'm looking forward to portlets so that i can support Nukes for my own sites and let the customers do as they wish. Until then, i think if you were to distribute a nukes module then you could be required to distribute the code as well, under GPL. So let's all do what we can do support development towards portlets... .joe