Let’s get this Windows Mobile, Symbian, Palm, RIM Blackberry comparison out of the way. The iPhone runs Mac OS X. That’s not a cut down version of Mac OS X. It’s the full thing, minus the usually bundled applications that you wouldn’t need to run on the iPhone. It has been heavily optimised and sits in less than 0.5GBytes of flash memory.

There’s concern that Apple won’t allow third party applications to run on the iPhone because of the possible disruption to the experience and the reliability of the device and of the Cingular network. The whole adoption of Mac OS X is a fundamental reason for this.

Now, I’m kind of okay with this, up to a point: the iPhone is the ideal platform for Widgets. Apple will probably bundle more widgets than they currently acknowledge existence of, but given the foundation of Widgets is likely to be CSS, HTML and Javascript, it’s practicable to open this aspect of the iPhone up to developers without risk of disrupting the overall experience. There is a major caveat to this: you can do things in Javascript that hog memory, CPU and there are potential memory leaks to account for.

With Mac OS X running on Macs, a developer gets pretty quick feedback from users if anything is wrong with their Widget. It’s also fairly easy to identify and shut down misbehaving widgets. This might not be the case with the iPhone, but Safari could stall due to a misbehaving website, or a bug or exploit in Safari, so something that permits corrective action to be identified and taken will be available.

What’s going to happen then? I think Apple will be the sole provider for fully-fledged applications (i.e. not Widgets), and frankly, if they’re anything like we’ve already seen, they’ll be great. Mac OS X Leopard will probably launch before the iPhone is released, which means all the new features expected in Apple Mail and iCal will be accounted for in the iPhone. Mac OS X Leopard should also include the long awaited Dashcode, Apple’s development kit for Mac OS X Widgets. It will be surprising if there aren’t starting templates for iPhone Widgets, together with guidelines for developing and testing on the iPhone. I also reckon that the iPhone will provide custom Javascript hooks into common gesture events.