For anyone who thinks I'm talking out of my ass, consider Qt. If you don't own the Qt copyright, you cannot sell Qt to a company who wants to use it to build a

For anyone who thinks I'm talking out of my ass, consider Qt. If you don't own the Qt copyright, you cannot sell Qt to a company who wants to use it to build a proprietary product - since Qt is GPL licensed, using it in a proprietary product would not be permitted. But since The Qt Company owns the copyright, they can sell their own software to companies that want to build a proprietary product with it - they just sell it under a proprietary license, specifically tailored for this. The fact that it was previously released under GPL is irrelevant, because the copyright holder can license it under as many licenses as they want. If you don't own the copyright to it, you can only """sell""" GPL software in a manner in which local DVD shops sold pirated movies back in the early 2000s.