Both the website and the project's Github repository loudly trumpet that they are "open source" next to photos of proprietary hardware.

In https://github.com/PetoiCamp/OpenCat-Old/issues/7, the creator admits that the "nyboard" (https://docs.petoi.com/nyboard/overview) at the heart of their robots is derived from Arduino, but insists that they don't need to comply with the licensing terms for derivative boards (https://support.arduino.cc/hc/en-us/articles/4415094490770-L...) because Arduino is unlikely to sue them.