[youtube]http://www.youtube.com/watch?v=AiEmwak1rIk[/youtube]
It would seem that Apple removed the restriction on registering the phone's UDID in a dev's account for iOS 4.0 GM, and now any compatible iPhone/iPod Touch can be updated to the new OS without any problem, of course the restore process ONLY works on Mac OSX and you need iTunes 9.2 which you can download from here.
This does not mean that iOS 4.0 GM works on iPhone 2G/iPod Touch 1G, but only that any other compatible terminal, excluding the iPad, can switch to 4.0 without any further hassles. Of course, it didn't last long and a method appeared to jailbreak iOS 4.0 GM on both iPhone 3G and iPhone 3GS. You have the solution for iPhone 3G here, for iPhone 3GS you only need to download the firmware bundles of here and replace them in PwnageTool in Contents>Resource>firmware bundles.
CAREFUL! If you need decoding, it's better to wait until the official jailbreak and decoding programs appear!
