As we reported earlier, several developers are looking to jailbreak the new iPhone OS 4.0 beta 4. Now Redsn0w has released its new version, redsn0w 0.9.5 beta 4 to jailbreak iPhone OS 4.0 beta 4 firmware. However, as the iPhone-dev team warns, this release is meant for the jailbreak app developers’ community, so that they can use the new OS, and fix their apps to work properly on the jailbroken iPhone OS 4.0 beta 4.

Note from the dev team:

This is a beta release of redsn0w targeted at developers of jailbroken apps. It uses the same pwnage2 DFU-mode exploit that we’ve been using since the 2.x days. Nothing new is revealed to Apple, and it’s not applicable to the iPad. Don’t go near it if you use yellowsn0w, ultrasn0w, or blacksn0w.

Because it’s meant for JB app developers, this beta redsn0w does not perform hactivation. You’ll need a properly-registered developer UDID with Apple to get past the activation screen. For similar reasons, there is no Windows version of this beta redsn0w (since apps are developed on MacOSX). Please don’t pirate Apple software.

YOU SHOULD STAY CLEAR OF THIS BETA SOFTWARE IF YOU RELY ON A CARRIER UNLOCK. That’s because the beta redsn0w works only if your device has already been upgraded to the stock 4.0beta1/beta4 IPSW from Apple, which contains a baseband update. If you installed that IPSW, you’ve already lost the carrier unlock until the next planned release of ultrasn0w and blacksn0w.

It is worth noting that  Redsn0w 0.9.5 beta 4 does NOT perform a baseband unlock for the iPhone OS 4.0 beta 4, which has a new baseband update. It is only a jailbreak tool. You can download the Redsn0w 0.9.5b4 from here.

Redsn0w 0.9.5b4 has limited support at the moment:

• iPhone 3G only (for now)
• Mac OSX only (for now)
• the 4.0beta1/beta4 FW only (for now)

The method for the jailbreak is same as for earlier releases.

This Jailbreak is meant for app developers’ ONLY.

Steer clear of this beta release if you rely on a carrier unlock, the beta redsn0w works only if your device has already been upgraded to the stock 4.0b1/b4 firmware from Apple, which contains a new baseband update. If you are using the new iPhone OS 4.0 b1/b4, you’ve already lost the carrier unlock until the next planned release of ultrasn0w and blacksn0w.

Method of install

• If you’re an old hand on iPhone development, then you’ve probably updated your iPhone3G to iPhone1,2_4.0_8A230m_Restore.ipsw, the steps after that are as follows:
• Launch the beta redsn0w 0.9.5
• Select your stock iPhone1,2_4.0_8A230m_Restore.ipsw file (you’ve already used this to update your iPhone3G to 4.0beta1)
• Select “Install Cydia” and click “Next”. Use DFU mode to install the jailbreak.
• When your iPhone wakes back up, you’ll see that Cydia has a blank icon, and no sources (I love beta bugs!)
• Go to the Sources panel and add this repo:

apt.saurik.com/cydia-3.7 (ignore all the network error messages)

• Now when Cydia restarts, you should see its usual logo, and the sources should be back to default.