Apple has released the fourth beta version of iPhone OS 4 for the iPhone and iPod touch, along with the accompanying SDK. As with prior beta releases, a main Xcode and SDK beta is available for download, as are pre-release builds of the iPhone OS 4 software for the iPhone 3G and 3GS, and the second- and third-generation iPod touch. Mac Rumors notes that the new beta version includes a new configuration page for Internet Tethering, and a special alert…