Supporters of OpenDocument say a single, open standard ensures long-term compatibility, allowing archived documents saved digitally in OpenDocument to be accessible in the future. They hope that the free format will eventually become as widely used as JPEGs and GIFs are in the graphics arena.

But the plan has drawn ire from some Massachusetts politicians, who think the state is interfering in the free market, as well as groups representing people with disabilities, who say OpenDocument fails, for example, to support text-to-speech features crucial to blind users as well as Microsoft Office does.

Microsoft, which claims Office has more than 400 million users worldwide, is supporting a new format native to Office 2007, OpenXML, which the company is promoting for acceptance as an open standard.

Alan Yates, general manager of Microsoft's information worker business strategy, said Microsoft welcomes the plug-in. "We have always expected that third parties would work on this set of issues and create bridges between the two sets of XML-based formats," he said.

Besides Edwards' plug-in, a New Zealand-based open-source project has developed free software that can convert Microsoft Word files into OpenDocument. According to its Web site, the software, called DocVert, "generally" works, though "some embedded objects within MSWord may not convert successfully." However, DocVert is not conveniently embedded into Microsoft Word, but is run separately.