MuscleNerd, a core member of the iPhone Dev Team focused on iPhone basedband hacking and unlocking  has posted the current status of the unlock for iPhone 4S. According to MuscleNerd’s post on Twitter, a “very iPhone 4S unlock is in the works”, just for the iPhone 4S”, not iPhone 4.
The unlock will work by installing UltraSnow from Cydia which allows iOS devices to get unlocked. Ultrasnow has not been updated since last year when unlock for iPhone 4’s baseband 01.59.00 was released.
(via iDowbloadBlog)