It’s the end of a dispute that began in January, when EC competition commissioner Neelie Kroes first voiced concerns about the software giant’s grip on the EU browser market. Kroes says the ruling will act as an “incentive for web browser companies to innovate and offer people better browsers in the future.”

In a statement, Microsoft SVP and general counsel Brad Smith says the company is “pleased” by the ruling, hinting at Microsoft execs’ desire to put all this firmly behind them. He also annouces a “public undertaking” to open up Microsoft software to make it integrate more easily with rival software products: developers—including open source developers—will get the technical docs needed to build cross-platform products using Windows, Office, Exchange and Sharepoint.

Microsoft doesn’t have to do this, but Kroes warned in 2008 that high-market-share software companies should disclose products’ technical specs to allow “interoperability” between software platforms. It marks quite a change in attitude for super-secretive and competitive Microsoft—one that will require a “significant change” within the company, Smith admits.

But lookout: if the company breaks these new rules, the EC could impose a fine of up to 10 percent of its annual revenue—in the 12 months to June 30 this year the company made $58.4 billion (£35.9 billion), so it could be left one hefty fine if it doesn’t follow the rules. In 2007 Microsoft was fined €497 million (£305.5 million) for breaking competition rules by tying its Media Player software to Windows and then and extra €899 million (£522/7 million) for not complying with an EC ruling.