Oracle has started charging £55 per user for a previously free Open Document Format plug-in for Microsoft Office.
The plug-in allows users of Microsoft Word, Excel and PowerPoint to modify and save documents in the Open Document Format (ODF), which is the format used by competing open-source office suite OpenOffice.org. Oracle is the primary sponsor of OpenOffice and is continuing to support the project after its acquisition of original founder Sun Microsystems in January.
Sun's website was updated on Wednesday to state the "Oracle ODF plug-in now requires a fee of $90 [£58] US per user to obtain a Right to Use (RTU) licence".
Oracle requires a minimum of 100 licences per order and is offering optional first-year support for the plug-in at a cost of £12.07 per user.
The enterprise edition of OpenOffice also costs £55 per user for a perpetual licence and offers additional features to the free version to tempt businesses, such as a software development kit and a Microsoft SharePoint connector.
The closed-source ODF plug-in originally added interoperability between the fledgling format and Microsoft's dominant Office suite, although Microsoft added native support for ODF 1.0 documents in last year's Office 2007 Service Pack 2. Oracle's plug-in remains the only way to get support for the ODF 1.2 format introduced in OpenOffice 3.2.
Users of the Ubuntu forums believed the move to start charging for the plug-in was aimed at large enterprises currently unwilling to upgrade to Office 2007. Some expressed concerns that Oracle might start charging for software related to some of Sun's other projects, such as MySQL, Java and Netbeans.
Oracle made £14.3bn in revenue last year. The company declined to comment when approached by ZDNet UK on Wednesday.