Purplera1n is a Jailbreak tool for iPhone 3GS running 3.0 firmware available for windows and Mac. With purplera1n there is always a possibility to get back to a jailbroken state, if the apple updates its baseband to fix the jailbreak.
Once that you’ve got your jailbreak done, you can then use the ultrasn0w utility from Cydia to unlock your iPhone 3GS. You can also use redsn0w to unlock your iPhone 3G. If you are looking to unlock or jailbreak your iPhone 3G S you are advised not to upgrade to 3.1
If you are facing any issue on jailbreaking iPhone 3G S just email purplera1n.support at GMail and attach your purplera1n.log file. Or call the purplera1n support hotline @ (650) 265-1210. You may follow George Hotz on Twitter here.
Download – [Purplera1n for Windows] | [Purplera1n (beta) for Mac]