1. Download the Samsung Galaxy S Unlocker for Mac from this here:

http://www.multiupload.com/9NEBR6FAKD



2. Mount the DMG and drag the folder onto the hard drive. DO NOT DRAG THE ICON WITH THE LOCK (the app). Once the file is finished copying continue.



3. Open the application with the lock. It should open a terminal window. Let it run for a few seconds and then it should show your unlock code within the terminal window.

4. Write down your unlock code.

5. Turn off your vibrant and insert a SIM card from another carrier and turn it back on.

6. The phone will ask for your unlock code. Enter your code and your phone is unlocked. Enjoy and have fun.

source: http://forum.xda-developers.com/showthread.php?p=7776555#post7776555