Microsoft today attempted to exorcize the interoperability bogeymen that have haunted it since it was first discovered to be using secret APIs 20 years ago, bogeymen that now quote European antitrust law at it and carry writs from the Court of First Instance in Luxembourg.

To avoid further confrontation with the European Commission, which opened a broad investigation of Microsoft’s interoperability last month, the company said it would voluntarily open up all the APIs and communications protocols in its biggest revenue producers now and forever.

To be clear, it said that these are the APIs and protocols “used by other Microsoft products.”

The decision applies to Vista, Windows Server 2008, SQL Server 2008, Office 2007, Exchange Server 2007, Office SharePoint Server 2007, the .NET Framework and future versions of these “high-volume” products, it said.

Microsoft also promised to document for free the notorious extensions that impact interoperability that it creates when it uses industry standards. It said it would license any patents that cover these extensions on reasonable and non-discriminatory terms at “low royalty rates.”

It did not define “low.”

Microsoft also accommodated the anti-Microsoft OpenDocument Format (ODF) that’s promising to create an endless row with the EC.

It said it would design new APIs for the Word, Excel and PowerPoint programs in its Office 2007 suite so that third parties could plug in non-Microsoft file formats and use them as defaults when saving documents.

It didn’t say when these new APIs would be ready.

Microsoft did say it would try to work more closely with the open source community by creating both an online Document Interoperability Initiative and a more broad-based Interoperability Forum.

The regulators at the EC reacted immediately to the concessions Microsoft outlined in a press release before it staged a conference call this morning.

They were highly suspicious in a jaded “reheated hash” kind of way.

In the statement they hung on their web site they said, “Today’s announcement follows at least four similar statements by Microsoft in the past on the importance of interoperability.”

The EC also warned that Microsoft may not escape its vengeance if it finds that Microsoft hasn’t been complying with EU antitrust rules on interoperability before now.

“In the course of its ongoing interoperability investigation,” it said, “ the Commission will therefore verify whether Microsoft is complying with EU antitrust rules, whether the principles announced today would end any infringement were they implemented in practices, and whether or not the principles announced today are in fact implemented in practice.”

The Commission made the point that Microsoft’s actions today don’t address the tying claims that it’s investigating separately.

Anyway, Microsoft said any API and protocol documentation would be published on its web site available to all and sundry free of any license or royalty fee.

It said it would start immediately with the 30,000 pages of client and server protocol documentation that it was ordered to share with competitors as a result of antitrust actions on both sides of the pond.

Until now it’s been making this IP available under a fee-based trade secret license through the so-called Microsoft Work Group Server Protocol Program (WSPP) and Microsoft Communication Protocol Program (MCPP). That structure is now all been swept away.

Other protocol documentation will take a few months to get up, it said.

Microsoft said it will covenant not to sue any open source developer for non-commercial implementation of the protocols. The patent licenses will cover commercial development, an avenue that is also open to enterprises that use implementations from a distributor that doesn’t have a patent license.

Apparently the open source community can expect a stream of invitations to labs and plug fests.

Microsoft said it’s being guided by the Interoperability Executive Customer Council that it set up in 2006 that includes representatives of 40 companies and government bodies.