Purplera1n for the Mac has just been released by GeoHot. It has basically the same instructions as the Windows version that you can find in this video tutorial.
You asked for it, and we delivered. I’m not a mac coder, so AriX and westbaer stepped up to do it. Check out AriX’s blog here. Download link on purplera1n.com, and thank AriX and westbaer next time you see them!
Also, some more payload stability improvements were made, and the windows version was updated to RC2a. There is no reason to run RC2a if you already have RC2 installed.
So again, if you can’t wait for the iPhone Dev-Team’s own jailbreaking tool for the iPhone 3GS, this is a great alternative—it’s easy and fast too!
Note: Many are reporting that this doesn’t work on Mac OS X Tiger… and like in the Windows version, Winterboard also doesn’t work.