AFAIK original Arduino hardware is not a copyright design, and has actually been improved upon for most deployments (ie. made cheaper) in China, eg. by replacing with cheaper UART chipset.
And the Arduino designers do not object to people copying the electronic design (even less so if there are design changes like substituting in a different serial chip). What they ARE objecting to is people copying the branding and graphics (down to the "made in Italy"): https://blog.arduino.cc/2013/07/10/send-in-the-clones/
Still, different serial chips mean different device drivers, so one product shouldn't be sold under the other's name.