Xpress Evaluation Board Source Code
Is the source code for the PIC18LF25K50 (USB programmer for the main PIC® on Xpress Evaluation board) available?
The original code is open source and posted on Github.
Note that the code needs to be customized for each different target microcontroller by changing/adapting the file. The source targets two devices: PIC16F18855 family and PIC16F171x family.