You can jailbreak the iPhone 4 on your own as it is legal and easy. You need to install the latest version of iTunes, and download the correct version of iOS 5. You also need to download the Redsn0w software, which will enable you to jailbreak the iOS device. You should know that when you jailbreak your device, it leaves you without a warranty once any complications occur. You can get the step by step procedure of how to go about the process at, http://secondblogger.hubpages.com/hub/How-to-Jailbreak-iOS-5-on-iPhone-iPad-and-iTouch.