While newer Arduinos and Arduino compatibles (including the Hackaday.io Trinket Pro. Superliminal Advertising!) either have a chip capable of USB or rely on a V-USB implementation, the old fogies ...

It’s a RISC-V microcontroller, completely open source ... the HiFive1 is significantly faster than the Intel Curie-powered Arduino 101, or the ARM Cortex M0+ powered Arduino Zero.