Microsoft has sent a revised proposal to the European Commission for the terms under which it will license Windows protocols to competitors to comply with last year's antitrust ruling against the company.

Microsoft believes it has addressed most of the concerns raised by European regulators, but the two sides continue to wrangle over half a dozen remaining issues, said Microsoft spokesman Tom Brookes. They relate partly to how Microsoft's protocols can be distributed with open source products, he said.

A Commission spokesman confirmed that Microsoft submitted its revisions in a letter last Thursday. The Commission is studying it closely to determine whether it meets its demands, said Commission spokesman Jonathan Todd. He did not rule out the possibility that Microsoft could still be fined $5 million per day for noncompliance.

The licensing request stems from the Commission's antitrust ruling against Microsoft last year, when it determined the software maker had abused its dominance in desktop operating systems to gain an unfair advantage in related markets. Among the sanctions imposed against the company, Microsoft was ordered to license certain workgroup server protocols to competing vendors to allow them to develop products that work well with Windows.

The idea is to prevent Microsoft from unfairly wielding its desktop monopoly to dominate the server market. It was also ordered to offer a version of Windows without its media player software and fined €497 million.

Last month the Commission rejected Microsoft's initial licensing terms for the protocols, prompted by complaints from the Free Software Foundation Europe that the terms were unfair to open-source developers. On March 21 the Commission gave Microsoft an informal two-week deadline to come up with better terms before it decided whether to fine it for noncompliance.

The Commission detailed 26 concerns with Microsoft's initial licensing proposal, Brookes said Monday. Microsoft has "accepted or offered proposals to address" 20 of those concerns, but the two sides continue to debate the remaining issues, he said.