Since it's launch there has been one persistent criticism of the iPhone and that has been its closed platform:

Apple made it very clear from the start that AT&T was going to be the exclusive carrier for the iPhone, and two weeks before the iPhone went on sale, CEO Steve Jobs let everyone know that because of security and reliability concerns, native third-party applications weren't in the cards for iPhone 1.0.

"We have been trying to come up with a solution to expand the capabilities of the iPhone by letting developers write great apps for it, yet keep the iPhone reliable and secure," Jobs told developers at the Worldwide Developers Conference in June. That solution was Web-based applications, which is sort of like being told that you can't buy a DVD because HBO shows that movie every month or so, and it was met with tepid applause by Apple's developers.

If you live in New York City (and especially if you ride the subway), you probably know that Nokia even launched an advertising campaign promoting the 'openness' of its phones, taking a jab at Apple.

Well, the walls are coming down:

Steve Jobs made it official Wednesday morning: third-party applications are coming to the iPhone.

Apple's CEO posted another of his open letters to the world Wednesday on Apple's Hot News section of its Web site, confirming reports that a software development kit (SDK) for the iPhone will be released to developers next year. It's coming in Februrary, rather than January as reported, but application developers and iPhone owners will probably be able to wait the extra month.

Why the change of heart?

It always made sense for Apple to go down this road, since it was never going to win a hacking war and users clearly want third-party applications on their iPhones and iPod Touches, which will also be opened up by the SDK, Jobs confirmed.

Head over to C|Net for more information about the SDK, including Apple's response to Nokia.