> If they want GPL except it's proprietary then they can do that.
Only if they don't use the text of the GPL to do that, as it's not a freely licensed work (more specifically, they'd have to use a different name, remove mentions of GNU and remove the GPL preamble to be able to use the rest of GPL as a base for their license).
Only if they don't use the text of the GPL to do that, as it's not a freely licensed work (more specifically, they'd have to use a different name, remove mentions of GNU and remove the GPL preamble to be able to use the rest of GPL as a base for their license).