There's plenty of forks already. See Adafruit, Sparkfun, and tons of others.

What's Arduino's IP look like?

They have the PCB files and schematics linked from here: https://store-usa.arduino.cc/products/arduino-uno-rev3 It says "Arduino Uno is open-source hardware! You can build your own board using the following files"

Found some licensing info here: https://support.arduino.cc/hc/en-us/articles/4415094490770-L...

Thanks! That doesn't seem like a tempting target for patent trolling (which wasn't your assertion).