Corporations choosing to not use GPL software mostly don't know enough about it, to know it's ok. So they ban it outright.
No, they might not. Just like Microsoft, they might demand that you don’t release your plugins. Addidionaly, GNU software gives you the alternative of releasing your plugins. But you don’t have to, and they can’t make you do it.
No, they might not. Just like Microsoft, they might demand that you don’t release your plugins. Addidionaly, GNU software gives you the alternative of releasing your plugins. But you don’t have to, and they can’t make you do it.