I0nic has given his untether for the iOS 4.3.1 jailbreak to the iPhone Dev-Team for testing and integration into their jailbreak utilities.
The iphone-dev-team is already beta-testing the untether. So it is up to them to give you your tool of choice.
Please don’t bother the dev-team now. The deal is: if the beta test is successfull, they are free to do whatever they want with it.
We’ll let you know as soon as we hear more!