Originally the Dev Team was going to hold off until Apple's 3.1 release of the new software, however they were forced to show their hand when Geroge Hotz posted his "purplera1n" unlock.
Here are the details of the unlock from the Dev Team Blog:
ultrasn0w unlockers — You all must remain particularly vigilant against upgrading your basebands, since doing so will kill the unlock (for most phones, there’s no going backwards in baseband version). Apple has gotten very serious with the latest baseband — they’ve removed 180 (!) commands in an effort to cut down their exposure to holes. So please always stay away from stock Apple IPSWs and instead use our tools as we release them. These tools let you update your firmware without updating your baseband.
Those installing ultrasn0w will probably also need to do a single run of Settings->General->Reset->Reset Network Settings. We’re testing various fixes for that particular glitch.
Once again, thanks to @Oranav for finding the new injection vector that allowed us to transform yellowsn0w for baseband 02.28 into ultrasn0w for baseband 04.26, and for not revealing it to Apple before it could be used where it would be most effective — firmware 3.0.
redsn0w platforms — This is the first redsn0w release that also supports linux! It’s the newest version of the bunch, so any feedback would be appreciated. But right now, redsn0w should work on OS X, Windows, and linux.
How to get the goods:
- The redsn0w torrent seeds are all here. Any direct mirroring help would also be appreciated.
- The updates to ultrasn0w, MobileSubstrate, and WinterBoard are all handled directly through Cydia (after you’ve jailbroken!)
- The Cydia repo for ultrasn0w is http://repo666.ultrasn0w.com (that last o in ultrasn0w is the number 0!)