Microsoft has finally agreed to comply with its obligations under the European Commission’s 2004 anti-trust ruling that required the software giant to open up access to its Windows operating system (OS).

Under the 2004 ruling, Microsoft was found to have abused its dominant position in the marketplace and blocked access to its OS by third-party developers. At the time, Microsoft was fined €497m (£350m) and ordered to disclose source code information that would enable third-party work group servers to fully interoperate with Windows machines. The ruling was recently upheld by the Court of First Instance, although Microsoft was offered an opportunity for a further appeal.

However, Microsoft has today agreed to provide open-source software developers with interoperability information for a one-off royalty payment of €10,000 (£7,000), according to the EC. Furthermore, the royalties for a worldwide licence including patents will be reduced from 5.95 per cent to 0.4 per cent, which is less than seven per cent of the original royalty amount. Microsoft will also offer guarantees to open-source developers that it will confine legal action over its patents to commercial software products. The deal was reached after a series of personal negotiations between European Commissioner for Competition Policy, Neelie Kroes, and Microsoft chief executive Steve Ballmer.

The EC said the terms of the agreement mean that businesses will be able to take advantage of “competitive, innovative alternatives” to Microsoft work group server products that are fully compatible with the Windows desktop OS.

“It is regrettable that Microsoft has only complied after a considerable delay, two court decisions, and the imposition of daily penalty payments. However, the measures that the Commission has insisted upon will benefit computer users by bringing competition and innovation back to the server market,” said Kroes. “[Microsoft] can no longer use the market power derived from its 95 percent share of the PC operating system market and 80 percent profit margin to harm consumers by killing competition on any market it wishes.”

If Microsoft fails to stick to the agreement, the EC warned that it can revert back to issuing daily penalties.