In a filing last night (PDF, 26 pages), California and several other states asked U.S. District Judge Colleen Kollar-Kotelly to extend most of Microsoft's U.S. antitrust settlement for another five years. The filing formalizes a request that the states previously outlined in court.

In arguing for the extension, the filing cites a number of concerns, including the fear that Microsoft could use the next version of Windows to "tilt the playing field" toward Silverlight, its new Adobe Flash competitor.

That plays into a broader debate over the extent to which Web-based technologies have diminished Windows' power. Here's what Microsoft said on that topic in an Aug. 30 filing (PDF, 12 pages), as part of its assertion that the final judgment in the case has been effective:

"The entire notion that developers were forced to write to the (application programming interfaces) exposed by Windows, and that this constituted a significant barrier to entry that protected the market position of Windows, is being called into question by the emergence of server-based applications that are operating system agnostic. Companies such as Google achieved major success after the Final Judgments were entered by offering client agnostic applications that are accessible over the Web."

Excerpts from the California group's new response on that issue:

"Because web-centric technologies are so dependent on web browsers and servers for access to consumers, they are particularly susceptible to impediments that Microsoft could interpose were the Final Judgment to expire now. Many of the "new" or "emerging" technologies cited by Microsoft's experts are dependent on a "standards based" browser to access computing functionality delivered by servers. ... For the vast majority of PCs, that browser is IE."

"A specific example of how vulnerable these 'new' or 'emerging' technologies are to manipulation by Microsoft, absent the continued protections of the Final Judgment, is offline internet-centric middleware such as Google Gears and the Adobe Integrated Runtime (AIR, formerly known as Apollo). Each of these recently introduced technologies enables consumers to use Internet-centric applications while offline (i.e, while not actually connected to the Internet) – thereby lessening their reliance on traditional applications.

"They represent a potential threat to Windows insofar as they are accessible by standards-based browsers from multiple operating system platforms, not just Windows. ... But should the Final Judgment expire now, Microsoft has the power to tilt the playing field towards its own technology, Silverlight. Microsoft has announced that its next client operating system, Windows 7, will arrive in approximately 2010. Were Microsoft to favor Silverlight in Windows 7 like it did its desktop search technology in the initial Vista release -- and as it could absent the protections of the Final Judgment -- the platform threat of competing products like Gears and AIR could be severely compromised."

Microsoft issued this general response to the California group's filing.

"As we believe, and the Department of Justice has stated, the consent decree has served its purpose, ending practices the courts found were anticompetitive, and providing additional legal remedies as well."

Key provisions of the 2002 antitrust final judgment are scheduled to expire Nov. 12, absent action by the judge in the meantime. The judge previously pushed back the expiration of some provisions, related to the licensing of Windows server protocols, by two years.

Update, 4:20 p.m.: On the subject of Silverlight, it's worth noting that it also works on Macs, and Microsoft has said it will be available for Linux.