At first when I saw this, I thought it was a new jailbreak, but as I dug around, it turned out to be a scam.  How do I know? I go to the iphone dev website to check, and there is was..

Update #3: Remember, there are scammers everywhere in the iPhone scene.  The latest one involves something called “ClawPack”.  Avoid this costly, untested, and certainly unendorsed ripoff of our free software.

Now, just to be clear, there IS a jailbreak for phone 4, and iphone 3G running iOS4.  You just have to make sure you are running the correct app.  And as always, remember you are taking your life in to your own hands when you jailbreak.   Here is the link to the dev pwnage tool page.