The current version can be downloaded here.
Before running or compiling the program, a java serial library must be installed. Obtain the most recent source tarball from http://www.RXTX.org. In this archive, there is a readme file for MacOS X. Follow the instructions in this file to install the library.
To compile the java program, type:
% javac avrjavaprog.java
To run the program (or to get the options), run
% java AvrJavaProg
My typical run looks like:
% java AvrJavaProg -p 4 object.rom
To access this program from any directory, copy this class and the shell script avr-prog to one of your bin directories, and then run (for instance):
% avr-prog -p 4 object.rom