In the latest challenge to Microsoft's dominance of the productivity software market, a group of Linux developers has begun testing an online version of a free office applications suite.

Developers at online software provider Ulteo said in a message posted on their Web site site that a hosted version of OpenOffice.org 2.3 that they plan to offer is now available for public beta testing.

The trial version of the software can be launched from within Ulteo's Online Desktop package, which is itself currently in beta testing. The Ulteo Online Desktop aims to offer users a range of open source, Web-based applications and services. The project is led by Mandriva Linux creator Gael Duval.

Would-be beta testers apparently can't wait to get their hands on an online version of OpenOffice. As of Monday, Ulteo was warning users that its Web servers are overwhelmed and that they might have to return later to access the program.

OpenOffice software is based on the Open Document Format, which has been certified as a standard by the International Organization for Standardization. The package, available as a free download, offers word processing, spreadsheet, calendaring and other types of applications also found in Microsoft's pricey Office suite.

By offering an online version of OpenOffice, Ulteo hopes to enhance its collaborative capabilities. For instance, online users of the suite will be able to work together on a document simultaneously and perform other coordinated tasks, Ulteo says.

OpenOffice isn't the only challenge to Microsoft's reign over the office productivity software market. Google recently entered the fray with an array of hosted applications sold as a service under the Google Apps brand.