The project demonstrates the programming of AVR microcontrollers on other boards with only the use of a USB cable and 6-pin IDC to 6-pin IDC cable since it is designed for production within a FabLab.
The Unified Program and Debug Interface (UPDI) is Microchip’s proprietary interface for programming and on-chip debugging, and has become the standard on AVR MCUs after Microchip’s purchase of Atmel.