pngdiet is a commandline PNG compressor
It was built out of necessity, to fix the display problem with Safari and ICC profiles. It removed ICC profiles from PNG files.
From there, it has evolved to become a full blown compressor.
pngdiet is a Ruby wrapper around some utils (pngcrush, pngrewrite) and runs on Mac OS X and Linux.
These details are provided for information only. No information here is legal advice and should not be used as such.