> You may argue that commercial FPGAs are also closed and while it's true, the principle of operation is so simple (lots of interconnected gates) that can be easily replicated, like this cool project shows.

Basic CPUs are not all that complex either, there are plenty of homebrew CPU projects made of discrete components. Both those and this project share the common trait that they are almost impossible to scale up to be useful.

I would also be very surprised if FPGAs aren't also heavily patented.