Fake-Operator is a project mainly written in C and OBJECTIVE-C, it's free.
Spoof your Operator on iOS 4.2 without having to edit PList's and without having to respring!
Fake Operator is a Mobile Substrate tweak built using Theos to dynamically change your iOS devices Carrier name.
You can either edit com.nspwn.fakeoperator.plist manually or in Settings.app