Instructions from gimgunlock thread:
Mac OS X version of gimgunlock v0.03
Usage: unzip, open a Terminal window and use either method below to unlock.

method 1:
enter the command below
"pathname-of-gimgunlock" "pathname-of-img-file-of-map"
hit return to run

method 2:
drag the icon of gimgunlock to the Terminal window
drag the icon of img file of map to the Terminal window
hit return to run.