Oracle has imposed a fee of US$90 per user on a plug-in for Microsoft Office that was available at no cost under Sun Microsystems' ownership.
The tool allows Word, Excel and PowerPoint users to read, edit and save documents in the ODF (Open Document Format), which is used by the competing OpenOffice productivity suite.
Sun, which was acquired by Oracle earlier this year, founded the open-source project that created OpenOffice.
Oracle continues to sponsor the project and sells two editions of OpenOffice in product form. A standard edition, meant for single users or very small companies, costs $49.95 per perpetual license. The enterprise edition, which requires a minimum of 100 users, adds features such as a Microsoft SharePoint connector and SDK (software development kit), and costs $90 per perpetual license.
A minimum of 100 users is also required to order the Office ODF plug-in, according to Oracle's Web site. In addition, customers who wish to receive upgrades in the future must also purchase a support contract, which costs roughly 22 percent of license fees per year.
The ODF plug-in is meant in part to provide interoperability between Microsoft's platform and ODF, which is backed by an lobbying group that counts IBM, EMC and Oracle among its members.
While Microsoft added support for ODF with the release of Office 2007 Service Pack 2 last year, Oracle's move could also be meant to snare business from enterprises that are reluctant to upgrade from Office 2003 but desire ODF compatibility, as some users noted on an Ubuntu forum.
An Oracle spokeswoman didn't immediately respond to a request for comment Tuesday.