No instructions on how to go from obtaining the source code up to the point of flashing the chip. We're supposed to guess how to do every step?
Instead of having compile targets in a Makefile, the readme advises scrupulous editing of the source code based on target chip. Sorry, but this requires that humans be careful and scrupulous, which sets the bar pretty high.
Parts of the documentation don't make sense. For example what does "LFUSE 0xE2 HFUSE 0xDF > internal oscillator" mean? That's not even a valid greater than statement.
Issues found: