Apple has changed the name of iPhone OS to “iOS” and has announced that iOS 4 will be available through iTunes for the iPhone 3GS, iPhone 3G, and iPod touch on June 21. Apple will also give developers access to the gold master of iOS 4 today in order to test their applications for compatibility.

My iPhone 3GS is registered as a developer device and I’m sure I’ll have access to iOS 4 shortly. I’ve been using Beta 4 for a few weeks and have been very happy with it. All of the features are fantastic, specifically the unified email inbox — it’ll change your life.

Update 6/8/10: I upgraded my iPhone 3GS to iOS 4 last night. It runs just fine and I can assure you that you don’t need your iPhone’s UDID to be registered in order to upgrade. The only catch is that you will need to have iTunes 9.2 beta installed to sync with your computer.

iTunes 9.2 seems to work just fine, I haven’t had any issues with it at all. And iTunes 9.2 is fast, really fast.