OS 4.0 has been Jailbroken on iPhone 3GS

Kaatje,an ex-Apple employee has posted a new post where she had done the jailbreak of iPhone OS 4.0 Beta 4, Yestarday we announced you by the redsn0w beta to jailbreak OS 4.0 Beta 4 but on 3G only, Oh another great something too is that the break doesn’t upgrade your baseband, and that means you can enjoy iPhone OS 4 jailbroken on the older baseband with an unlock using ultrasn0w.

Here's what she says in the post where she patched various files in the firmware, and then it makes a custom firmware to restore it using iTunes on iPhone 3GS (just as Redsn0w and Pwangetool)..

This is a work in progress but I thought I would share the results so far. Cydia still has some issues, many applications install but crash, some examples include mobileterminal, sbsettings, five icon dock. I did this only to hopefully motivate the developers to get their applications ready for 4.0 as it is coming very soon and the last thing we need in the community is to have repos full of broken apps! I accomplished this by patching asr, lockdownd, LLB, iBEC, IBSS, iBoot, kernelcache, MobileSafari, Services.plist, and fstab. The binaries were patched with IDA Pro and OxED and were then diffed against the original pwned files with bsdiff to create patch files. I then took the diff files and built a firmware bundle that I dropped into Pwnagetool and updated the cydia tree within Pwnagetool as well. Once this was done, I created a custom ipsw with Pwnagetool, unzipped it, applied a pwned LLB from a pwnagetool generated 3.1.3 ipsw, zipped it back up and restored to my device. At this time I am unable to get my T-Mobile NL sim to work so I downgraded back to 3.1.3 after playing around with 4.0 for a while. I look forward to the release and the official unlock from the Dev-Team. Many thanks to @p0sixninja for many hours patiently showing me the tricks and tips of jailbreaking 4.0b3 and then setting me out on my own to do beta 4. Without his tutelage, this would not have been possible :)

But she didn't give a Time for arrival of the release, I guess this method will be integrated to the new PwangeTool to Jailbreak the Final Version of the iPhone OS 4.[via Redmondpie]

Currently, You can jailbreak your iPhone, iPad, iPod on OS 3.1.3 Using Step-by-Step Guide to Jailbreak Using Spirit from Here.