Recently, planetbeing (from the iPhone Dev Team) had unlocked the newly released iPhone 4. Apparently there is more than one way to exploit the baseband OS for the iPhone 4 as Musclenerd has unlocked it as well using another method (out of 3 possible methods)

As you can see below, the iPhone 4 is running on another carrier instead of AT & T i.e it has been unlocked.

The two hackers are working together to get the next version of ultrasnow out with support for the iPhone 4 as soon as they decide on which exploit is faster and trouble-free for normal use.

Source