Despite Microsoft's concerns that the rise of ODF could prove problematic for Office in the marketplace, Edwards said Microsoft was very helpful with his development efforts. Microsoft has "the best third-party developer model," he said. "They gave us what we needed, and it works beautifully."

Sun, meanwhile, said it can't guarantee that its plug-in will be able to save to ODF by default because of "information about the MS Office application that is not generally available."

"Our technical engineers feel that the ways for accessing the range of interface options in Office [are] not fully documented and fully committed to," said Douglas Johnson, corporate standards program manager at Sun. "We don't think Microsoft Office is too proprietary. We know it is."

Sun also said that it may not be able to guarantee that Office files converted to ODF retain all of their formatting and other information due to "technical or intellectual property-related reasons" related to Microsoft.