redsn0w 0.9.15b3 for Mac was available as a free download on our application library. Our built-in antivirus scanned this Mac download and rated it as virus free. This free software for Mac OS X was originally designed by iPhone Dev Team. The program lies within System Tools, more precisely Plugins & Addons.
From the developer:
A cross-platform jailbreaking, unlocking, and customizing tool for iPhones and iPod touches. Customizations include boot logos, recovery logos, and "verbose" boot. It's a standalone program that doesn't use iTunes (no custom IPSWs are involved).
Apple Firmware 4.1-5.1.1 supported. Hardware supported. iPhone 3GS iPhone 4 iPhone 4S iPod Touch iPad iPad 2 iPad (3rd generation)
You may want to check out more software for Mac, such as Significator for iTunes, which might be similar to redsn0w.