they do have a free version of protool.
http://www.digidesign.com/ptfree/
supercollider is also free now, just google it, you should find it easily.
you can run max/msp on mac, but the program and other add-on programs are not cheap.
there are other softwares that got mentioned somewhere else, check them out as well since I don't know what you really want and need.
they are:
PlayerPRO, tractor for Mac I think.
http://www.soundhack.com/
the rest, not sure if they run on mac:
Buzz
Smart Electronix VST's
Bidule
Synth Edit
Audio Mulch