You've got a microcontroller that is ostensibly open-source hardware, but it's using a component from a company that most definitely swings hard in the other direction.
Microcontroller != development board.
The chip itself is (I assume) open source. The implementation of this specific development board was created using proprietary software and includes a proprietary component, but that's about it.
If the MCU is of any interest to people, there will be other more or less open dev boards created. Most obviously would be things like the STM32 ARM boards that are all over the place now having just the minimum voltage regulation, resistors, capacitors, pin headers, crystals and jumpers to be usable with an external USB-to-TTL conversion module.