Update: Microsoft says that Steve Ballmer will not be appearing at Apple's WWDC Conference. "Steve Ballmer not speaking at Apple Dev Conf. Nor appearing on Dancing with the Stars. Nor riding in the Belmont. Just FYI," the company said in a post to Twitter.

Microsoft CEO Steve Ballmer will take a seven-minute segment of Steve Jobs' Apple Worldwide Developers Conference to announce that his Visual Studio 2010 software will compile native Mac OS X and iPhone OS applications.

On the same day, Satan will be calling out the gritting lorries.

Well, that's what we thought when we first heard this, but according to Global Equities Research analyst Trip Chowdry - by way of Barrons - Ballmer is going to make just such a statement on 7 June.

It's a claim that's worth closer consideration. What's interesting here is not merely that Microsoft might out get onto the iPhone bandwagon, but that it's doing so with Jobs' blessing.

And, given Apple's argument with Adobe over the way iPhone applications should be developed - Apple says they must be native; Adobe wants to use its own frameworks - may yet lead to legal fisticuffs, Ballmer's move may even have come at Jobs' bidding.

The tighter Apple controls the iPhone application development process - and right now you can't even write your own app to run on your own phone without paying $99/£59 a year to Apple and agreeing to its lockdown non-disclosure and licensing agreements - are going to draw the attention of antitrust agents sooner or later.

It's already happening with iTunes: US trade officials are reportedly looking into the way Apple has grasped so much of the music market - 70 per cent of US download sales; 30 per cent of US music retail period, according to market watcher NPD. As Apple becomes increasingly this decade's The Bad Guy, it is only going to draw the attention of regulators even more.

Apple certainly has arguments ready to justify all it does, but you see senior command feeling the need to make some concessions before matters really get out of hand. It will clearly do its utmost to retain control of the App Store and ensure it stays the only mass-market iPhone/iPod/iPad software distribution channel, but is there anything it can do to be seen to be putting less limitations in the way of developers?

Right now, if you want to develop iPhone OS apps you need Apple's tools and Apple's computers. Good though they are - this reporter is happy to do his programming in Xcode - this is an area Apple can be more accommodating. Before the advent of Mac OS X, there were a handful of high-level language compilers for the Mac. RealBasic is still around but it remains a minority interest and is of no use to iPhone coders.

What better for Apple to stress its 'openness' by not only allowing third-parties to create iPhone OS development tools but for the first of them to be the old enemy - a company that now has a smaller market capitalisation than its arch-rival?

Especially since both firms are well aware that the real enemy is one they both face: Google.

At a stroke, Apple gives a concession to existing developers and enables many more to get working on its key new platform, the iPad; looks to regulators to be less of a threat to free markets; and shows it's now more important than Microsoft. Now, why wouldn't Jobs go for that? ®