BRUSSELS, Jan. 25 — Facing daily fines from European regulators, Microsoft said on Wednesday that it would license some of the source code for its Windows operating system to competitors.
The move is an attempt to comply with a ruling by the European Commission in March 2004 that Microsoft had violated antitrust laws. The company was fined 497 million euros (about $600 million) at that time and ordered to share details of its operating system with rival software makers.
The company generated 12,000 pages of technical documentation, but the commission was not satisfied and filed a new lawsuit against Microsoft in December, accusing it of failing to supply the information the commission had demanded and of charging too much for the data it was offering. Microsoft has until Feb. 15 to reply to the objections.
Under European antitrust rules, regulators were threatening to fine Microsoft up to 2 million euros a day if it failed to comply with the ruling.
The decision to allow access to some Windows source code aims to address "categorically" all of the issues raised by the commission last month, Microsoft said in a statement.
"Today we are putting our most valuable intellectual property on the table so we can put technical compliance issues to rest," Bradford L. Smith, Microsoft's general counsel, said at a news conference in Brussels.
The company will offer licenses to examine the code that controls communications between servers, which rivals could use to develop Windows-compatible software. The rivals will not be allowed to copy the code and it will not be available for open-source platforms, like Linux.
"We're not open-sourcing Windows," Mr. Smith said.