UPDATE: This edition of redsn0w does not perform hacktivation. Unless your UDID is validated with Apple, you will be unable to use this firmware. If you rely on carrier unlocks, do not use this version of redsn0w.
The iPhone Dev Team has successfully jailbroken iPhone 4.0 beta 1 and released a public release via Twitter solely for the purpose of jailbroken developers preparing their applications and extensions. Even if you’re not actively developing and would like to use this edition of redsn0w for a jailbreak, you can grab it here. The release supports only firmware version 4.0 beta 1 on the iPhone 3G. It is available exclusively for Mac OS X.