Apple is tearing down the obstacles to broad third-party development on the iPhone, but that doesn't mean the computer maker is offering a free-for-all.

Apple on Thursday released in beta the same software development kit its own developers use for building applications for the smartphone. Starting in June with the release of the next version of the iPhone operating system, applications built with the SDK will be able to access application programming interfaces in the entire iPhone software stack.

While the technology will give independent software makers everything they need to build quality software for the iPhone, Apple said it plans to maintain tight control over what goes on the device through distribution.

With the exception of custom applications built by corporations solely for the use of iPhone-carrying workers, all software built will have to be offered through Apple's App Store. If developers don't want to use the store, "then they won't be able to develop applications for the iPhone," Apple chief executive Steve Jobs said in answering reporters' questions following the unveiling of the SDK at the company's Cupertino, Calif., headquarters.

Nevertheless, Jobs promised software distribution terms easy on developers' pocketbook. "We don't intend to make money on the Apps Store," he said.

To cover costs, Apple plans to take 30% of the revenue generated from the third-party software it distributes. Developers set the price of their own software. If the application is offered at no charge, then Apple will distribute it at no charge, Jobs said.

"You know what price a lot of developers pick? Free," Jobs said "When they want to distribute their app free, there's no charge to distribute free apps. We'll pay everything to get those apps out there for free. Will there be limitations? Of course."

While Jobs called the iPhone platform a financial "boom for developers," how lucrative the device becomes will depend on whether Apple meets its sales goals. The company expects to sell at least 10 million iPhones by the end of the year. In the fourth quarter, the iPhone was second in terms of smartphone shipments in the United States, behind Research In Motion's BlackBerry.

Before software can be uploaded to Apple, developers will have to pay $99 to join the company's developer program, which will offer tech support and SDK updates. Apple will generate an electronic certificate to identify each developer, so malicious software can be tracked to the creator. Apple will also be able to take down an application it believes is a threat to iPhone users.

Apple's goal is to distribute as many applications as possible, with some exceptions. The company won't distribute software that carries pornography or invade a users' privacy, Jobs said. As a nod to carrier partners, Apple will only distribute Internet telephony applications that use the iPhone's Wi-Fi connection, not the cellular network.

Apple's SDK and distribution plans will apply to the iPod Touch, which uses the same operating system as the iPhone, but can't access a cellular network. The device, however, can access the Internet over a Wi-Fi connection.

A new version of the iPod Touch OS will be available at the same time the iPhone is upgraded. The former, however, will cost the user a "nominal fee," Jobs said. "We'll set [he cost] when we release the software for the iPod Touch in June," he said. "[But] we don't view this as a revenue opportunity."