Neither GreenPosi0n nor Limera1n are unlock tools, both are jailbreaks only. There is no unlock for the latest baseband, and may never be. All previous basebands can be unlocked, e.g. with UltraSn0w. If you want 4.1 with unlock, wait for Pwnage Tool to be updated to use SHAtter/the Limera1n exploit, and use it to update without updating baseband.