I got blink to compile under 0018 on the Mac
I downloaded the butterfly files from http://stuffthingsandjunk.blogspot.com/2008/11/arduino-for-butterfly.html
I put the folder in
I deleted everything except the butterfly entry in boards.txt
I had to make these changes
rename main.cxx to main.cpp
add #include <WProgram.h> to main.cpp
I do not have a butterfly to check out to see if it works.
I tried compiling a couple of programs, anything that used TWI (I2C) does not compile.