Unlocking the iPhone, or using the Apple’s fans jargon, iOS iphone jailbreaking, is the process of removing any limitation to the use of an Apple’s device. It allows you to install whatever you want on your device. iPhones are certainly among one of those devices that can be jailbreaked. After jailbreaking your iPhone, you’ll still be able to use the App Store and iTunes.
Unlock iPhone is legal in the US and Europe. If you are in any other jurisdiction, check the law before you jailbreak your iPhone. After it’s done, you still be able to restore your old operating system through the normal means (ie. using iTunes).
Remember that unlocking iphone can mean both jailbreaking and SIM unlocking. As a matter of fact, most iPhones in the US are not SIM locked, so there is often no need for unlocking it under this aspect.
The main reason to unlock an iPhone is to use iphone applications that are not available thought Apple’s platform. Many of these applications are banned. An additional reason is to tether using an iPhone (that means, connect several computers through your iPhone). The main reason for unlocking, in the sense of SIM unlocking, is to use other telecom carriers.
iPhone Unlocking can be performed easily with a computer and the appropriate software. Software for unlocking an iPhone is generally available 2 or 3 weeks after the release of any iOS version. However, the last iPhone 4 release, the iPhone 4.3 has not being totally jailbreaked. Under certain conditions, any unlock attempt will fail.
There are several providers in this segment: iPhone Dev Team, Firecore, Chronic Dev Team, or ih8sn0w are just the main players, which delivered consistent results in the past. Their respective software solutions are: redsn0w, seas0npass, Greenpois0n, pwnageTool, and Sn0wbreeze. Not all software solutions will work with any iPhone, since some locks are also dependable on the SIM, and some iPhones are the CDMA model, whereas others are the GSM model.
Also consider that Apple is making it difficult to unlock its iPhones. Imposing restrictions to their users is a huge source of income for Apple, sometimes even bigger than the sell of iPhones. Each new version seems to be more difficult to unlock. So, if you need a SIM unlocked phone, consider buying one unlocked at the first place. And if you need a completely free iPhones, probably you will have to go to a professional unlocking service.