TechWay

The iPhone Dev-Team has released a jailbreak of iPhone OS 4 beta 4 (redsn0w 0.9.5b4) intended solely for developers of jail broken applications. Since this release is only meant for developers, this version of redsn0w only works with Mac OS X and iPhone 3G devices that are registered with Apple’s developer program.

If you meet those requirements, and you’re willing to risk bricking your iPhone, follow  how to jailbreak iPhone OS 4 beta 4 after the break.

Steps 1 and 2 are only if you are not using a beta build of iPhone OS 4. Skip them if you have iPhone OS 4 installed on your device already.

Step 1: Activate your UDID with a Apple developer account to install iPhone OS betas. You will be stuck at the Connect to iTunes screen forever if you ignored this step.

Step 2: Install iPhone OS beta 4 (Beta 1 will still work, but isn’t advisable) by Option + left clicking on ‘Restore’ and selecting the beta firmware once prompted.

Step 3: After you’ve finished installing and syncing your iPhone again, open redsn0w (download can be found at the source link below) and click browse on the first screen. Navigate and select your beta firmware that you used to restore your phone. From this point on, it should be very similar to how you jailbreak on iPhone OS 3 using DFU. Follow this guide for more instructions.

Step 4: You should be done! Cydia should be there, but with a white icon and no repositories added. Add the following repository to use the standard sources and get the normal icon back: http://apt.saurik.com/cydia-3.7

Source: iPhone Dev-Team