IBM Targets Microsoft's Office Franchise

"The idea that someday IBM is going to send them a bill slows them down," Enderle said.

By coming out with a support option, IBM is answering an important corporate objection to open source products, Webster said.

Open source software "has not made much of a dent against Microsoft Office" because of the lack of a big vendor behind it, Webster said. "IBM is putting the power of its brand behind this, and now support as well."

IBM points to Microsoft's commitment to make its documents compatible with the Open Document Format as a way to allay corporate fears that Symphony won't let them communicate with their clients who use Microsoft-based products.

But that won't help much with the thousands of documents already created, Enderle said. Older Microsoft documents would have to be manually converted to ODF, a cumbersome process. That issue would become irrelevant with time, he added.

Companies have accepted Google Apps, which is offered free as hosted software, because it is popular with employees. But the economic model behind it -- users being subjected to advertising -- "is probably going to make it less palatable," Enderle said.

Both Microsoft and IBM have to contend with Adobe(ADBE Quote), which has moved into the office documents territory with the launch Monday of Acrobat.com, which provides word processing and Web conferencing services that are integrated with its PDF document software.

"Both Google and Adobe have a unique advantage in the Microsoft space," Enderle said. Creative companies are accustomed to using Adobe to create Web content, videos and pictures. "They may find an affinity for this product that may be increasingly similar to other Adobe offerings," Enderle said. And Google gives its Apps an edge by making them available across the Web as a free service, he added.

IBM was up $1.58, or 1.2%, to $128.94 in recent trading. Microsoft was up 24 cents, of 0.9%, to $28.03.