I started down the road of patching the code so that it can be compiled by a modern AVR GCC and libc, but eventually discovered that someone had already done it.
I then went on to find the original home of the code. He has a 1.7 version of the code,
EDIT: Turns out the patch was unnecessary... I was trying to build from the 'spi' directory, but the correct place is the 'usbtinyisp' directory. That has the correct pin assignments and requires no modifications. Just 'make' and reflash. Joy!