This project is not using LUFA, they are using another USB stack (I didn't know this one) and it claims to be smaller and simpler than the well know LUFA above
And yes, I found the g-code sketchup plugin here.
- LUFA is an open-source complete USB stack for the USB-enabled Atmel AVR8 and (some of the) AVR32 microcontroller series, released under the permissive MIT License (see documentation or project source for full license details).
- V-USB is a software-only implementation of a low-speed USB device for Atmel’s AVR® microcontrollers, making it possible to build USB hardware with almost any AVR® microcontroller, not requiring any additional chip. USB 1.1 for low speed devices - only about 1150 to 1400 bytes code size
- Turning an Arduino into a USB Keyboard