Let me clear this up straight. No, the phone you see in the screenshot is not a jailbroken iPhone 4, but rather a jailbroken iPhone 3GS, running iOS 4. The iMovie app you see is basically a “broken” port which was being tried to run on non-iPhone 4 devices but had issues in the end.
The following step-by-step guide will help you enable full Internet Tethering option in iPhone 3G and iPhone 3GS running the new iPhone firmware 3.1.2 without having to rely on any third party app for this functionality. For those of you who dont know, Internet Tethering is a process which enables you to use your iPhone as a wireless modem to share its Internet connection with a computer via USB cable or Bluetooth interface.