Apple has released a second version of its iPhone SDK. It is available immediately as a a 1.3GB download to registered developers on Apple’s developer site and it features Interface Builder, Xcode IDE, Instruments, iPhone simulator, frameworks and samples, compilers, and Shark analysis tool.

"We've also added new sample code and updated documentation to the rich set of resources available to you in the iPhone Dev Center," the company said.

The Apple SDK ships with firmware 1.2, which can be run via an emulator. Firmware 2.0, with all the enterprise functionality, was only made available to corporate testers already installed on real iPhones.

The iPhone 2.0 beta release includes both the iPhone Software Development Kit (SDK) as well as new enterprise features such as support for Microsoft Exchange ActiveSync to provide secure, over-the-air push email, contacts and calendars as well as remote wipe, and the addition of Cisco IPsec VPN for encrypted access to private corporate networks.

A crucial feature is the AppStore, which is included in the iPhone 2.0 software. It is a new application that lets users browse, search, purchase and wirelessly download third party applications directly onto their iPhone or iPod touch. Practically, every developer can submit its applications to the AppStore; Apple would retain 30 percent of all sales revenues, too much some have claimed.

The first beta of the iPhone SDK was unveiled by Steve Jobs on March 6, during an event held at the company’s headquarters. Shortly after the launch, Apple announced that the iPhone SDK has been downloaded ober 100,000 times. The final version of iPhone SDK is scheduled to be released in June, most probably at Apple’s WWDC.