Throughout the 5-year-old Microsoft antitrust case, one of the chief potential rivals to Windows' dominance cited in court arguments has been Linux. And that was true again this week, when opponents of the 2001 Bush administration settlement with Microsoft returned to appeal that ruling.

The sole holdout state, Massachusetts, asked the court to impose remedies that it contends are needed to help Windows rivals, which essentially means Linux. The state, which was the first to seek action against Microsoft, wants the settlement to require the Microsoft Office suite to be ported to Linux.

"In today's environment, Office is the (key) to the barrier of entry for commercial users," said Steven Kuny, the attorney representing Massachusetts at a U.S. Court of Appeals hearing last week on the settlement.

That's not all Massachusetts wants. Its remedy proposal would also require an open-source version of Internet Explorer, as well as provisions to ensure that Windows includes Java.

Two trade groups, the Computer & Communications Industry Association and the Software & Information Industry Association, which represent Microsoft's competitors, are also challenging the settlement.

Pointed questions
Whether the court will send the case back to US District Judge Colleen Kollar-Kotelly is the current question. The six judges who heard arguments were dispassionate but pointed in their questions, focusing on issues that have been central to the case: the commingling of Internet Explorer's code with the operating system, the adequacy of application programming interface disclosures needed to ensure application interoperability with the Windows operating system, and whether the remedy addressed any gains by Microsoft from its anticompetitive conduct.

Bill Claybrook, an analyst at Aberdeen Group in Boston, said porting Office to Linux would give the open-source operating system a big boost because of the importance of Office in enterprises.

"I think you would see a huge uptake in Linux use on the desktop," he said. Microsoft would still be owed a licensing fee, but even with that, Claybrook believes IT managers would be more inclined to consider Linux.

The judges spent little time on the government's argument that courts usually give deference to government anti-trust settlements, said Bob Lande, an antitrust professor at the University of Baltimore School of Law, who took that as a sign that the court is taking a new look at some of the issues in the case. "I think the settlement is in doubt," said Lande.

Tom Reilly, attorney general of Massachusetts, said after the hearing that Microsoft wasn't held accountable by the settlement with the Bush administration. "They still don't get it," Reilly said of Microsoft. "They don't think they have done anything wrong."

But Brad Smith, Microsoft's general counsel, said the company has acknowledged the court findings about its actions. He also said Microsoft has "been very clear in rebuilding and refashioning our relationship with the rest of the industry."