First to address the readme. Their goal for switch to GPL for closed devices is kind of pointless. For a closed device, they can still use it without modification. And even if they do modify it, how would you know. How would you prove it's your codebase they modified? The GPL does little to protect small projects. If they made money and got caught, they can just pay their way out of it. If they didn't make any money, well, no one would have probably found out until they they were a defunct company or the product was cancelled.
Second, more on the delusions of grandeur. Let's be real, this project is a small project with very little chance to grow big. It might become the defacto X server for old tech, but I doubt it would be used for anything new. And even if it is, not for many. The GPL won't protect it because it's obscure.
The GPL works for big high profile projects, like the Linux Kernel. It worked in the past because companies hadn't figured out a way around it, or that they can just ignore it and deal with the consequences later. They usually get away with it too, with little cost to them, as they have made their money.
I personally avoid releasing any of my projects as GPL. Because the likelihood of any of my projects being huge is minimal, and if they go big, I can change the license then. Maybe a non open source license like the Fair Source License that then transitions to MIT or Apache after 1-2 years.