The source code is available on Github.
It was coded with the PCW compiler by Custom Computer Services and using the included USB libraries.
The firmware contains a bootloader that allow you to reprogram the PIC through the USB connection, without the need of a dedicated PIC programmer.
To enter bootloader mode, you need only to keep the button pressed when you connect Type4me to your PC: the LED will stay turned on and the PC will detect it as CCS CDC Bootloader:
You can use the free ccsbootloader.exe utility, downloadable from Custom Computer Services website, to upload a new firmware: enter the correct COM port (in my example COM18) and your .hex file path:
A particular thanks to Embedded Adventures to have published schematics and source code for their USB2Serial Platform project: it’s a very good and cheap demoboard for PIC 18F14K50.