Regulators in Europe said Tuesday they will watch closely to make sure Microsoft complies with its commitments to ensure competition in the browser market, after Mozilla complained its Firefox browser is being excluded from Windows RT.
However, the European Commission noted that an agreement it struck with Microsoft in 2009 to regulate its behavior applied only to "client PCs," and it wasn't immediately clear if that incudes tablets, one of the main targets for Windows RT.
Mozilla protested last week that Windows RT, the version of Windows 8 for devices that use ARM processors, restricts choice and might violate an agreement Microsoft struck with the Commission to resolve an antitrust probe of the company.
Windows RT grants full access only to Internet Explorer (IE) and effectively blocks other browsers from accessing important functions, according to Mozilla. Its complaint was backed by Google, which makes the Chrome browser.
"The Commission is aware of these allegations and will remain vigilant that Microsoft fully complies with its commitments under the Commission's 2009 decision on browsers," Antoine Colombani, the Commission's spokesman for competition, said via email Tuesday.
"This decision applies to Microsoft's Windows operating system for PCs," he added.
E.U. antitrust regulators struck a deal with Microsoft at the end of 2009, ending an antitrust investigation of its dominant position in the browser market.
Since then, Microsoft has been required to display a ballot screen in Windows with links to other browsers including Google's Chrome and Mozilla's Firefox.
The Commission wouldn't say Tuesday if it believes Microsoft is violating the terms of the agreement. However, Colombani emphasized that the 2009 decision "doesn't go any further" than PCs.
Windows RT is intended primarily for tablet devices, but the OS will also be able to run on PCs that use ARM processors, according to Microsoft.
Microsoft may have decided it's debatable whether the 2009 browser agreement applies to Windows RT, said Roger Kay, an analyst at Endpoint Technologies. That might be a risky bet, he added. "If they are wrong then they basically will get their wrist slapped," Kay said.
Microsoft declined to comment Monday on whether it thinks it's required to offer a ballot screen in Windows RT.
Microsoft's agreement (PDF here) with the E.U. is legally binding and was set for five years. Microsoft could be fined up to 10 percent of its annual revenue if it fails to comply.
Loek covers all things tech for the IDG News Service. Follow him on Twitter at @loekessers or email tips and comments to email@example.com