The news that Microsoft has decided to open up its APIs has caused a seismic shock.

In fact, the about-turn in Microsoft's attitude to open source probably won't be replicated until Ian Paisley resigns to become papal nuncio and Paris Hilton decides to do her shopping at Wal-Mart.

Let's remind ourselves what Microsoft CEO Steve Ballmer had to say about open-source companies just two years ago. Accusing Linux users of infringing on Microsoft intellectual property, he made a covert threat that the company could even sue: " We believe every Linux customer basically has an undisclosed balance-sheet liability." Just two years earlier, fired off a memo pointing out that Microsoft's proprietary approach scored over an open-source one, every time. Now, the very programs that Ballmer claimed were top of their class and that were picked over by the open source vultures, will now be open to all.

Of course, sceptics are having a field day on this; pointing out that Microsoft's new-found openness coincides with a crucial ISO vote on Open Office XML - a ballot that is particularly critical to Microsoft - and during the company's entanglement with the European Union on a long-running anti-trust case. Indeed, the European Commission put out a statement saying that "The Commission would welcome any move towards genuine interoperability. Nonetheless, the Commission notes that today's announcement follows at least four similar statements by Microsoft in the past on the importance of interoperability." An indication perhaps that the company would have go a lot of a way further to satisfy the Brussels' bureaucrats.

But, it strikes me that this is slightly different from a lot of Microsoft statements in the past. It's true that there's a lot further to go and, given the company's history, it's as well to be sceptical.

For while the company has previously paid lip-service to words like 'co-operation' and 'openness', there had been very little evidence of the change. It seems that the more the company talked about being open, the less it was likely to be so - rather like the way that countries that had the word 'democratic' in their name were always likely to be the totalitarian ones.

It's true that the timing of the announcement is propitious to Microsoft - it certainly won't hurt its chances at next week's ISO vote - but I think that this goes deeper than a tactical move; the company is powered by smart people who see which the wind is blowing and now that the model of proprietary software, zealously guarded by an army of lawyers is not the way that the computer industry is shaping up. I'm not saying the Microsoft is going to be an enthusiastic adopter of everything open source; far from it - the lion may lie down with the lamb but I can't see Steve Ballmer palling up with Richard Stallman just yet - but I sense that this is the first tiny glimpse of real change.

Let's not forget there's another factor too: the G word.

In a few years, Google has gone from being a sophisticated search engine to becoming a behemoth to rival Microsoft -albeit one built on open source. Now, for the first time for years, there's been an industry bogeyman from outside Redmond. It certainly won't harm Microsoft's chances in any future struggles with the company to be seen as less proprietary, as more co-operative, as less, well, Microsoft-like.

Or perhaps, with Bill Gates' retirement from the company drawing near, the company is celebrating his departure with a grand gesture, something to remember him by before he spends his days on this charity foundation and playing bridge with Warren Buffet.

Whatever the motivation, Microsoft's move has certainly shaken up the software industry. Maybe the company won't quite bring itself to deliver on its promise - but if that is the case, I can see it being squeezed on all sides in the coming months. Or maybe, it has genuinely seen the light; the landscape next year could look very different.