The European arm of the Boston, Massachusetts-based free software advocacy group is making the move to add industry muscle to the EC’s case in light of Microsoft’s settlement with former antitrust competitors, according to Georg Greve, president of FSFE.

The more Microsoft is able to purchase its opponents’ solidarity, the more important FSFE’s commitment to freedom and interoperability is, he said in a statement announcing the application to intervene in the interoperability sanctions appeal.

In October, Microsoft settled its antitrust differences with media player rival RealNetworks Inc, paying $460m in cash up front as well as $301m in cash and services for 18 months in support of Real’s product development, distribution, and promotional activities.

The settlement put an end to RealNetworks’ private antitrust lawsuit against Microsoft but also weakened industry backing for the European Commission’s case after Microsoft settled antitrust differences with the Computer & Communications Industry Association and Novell Inc a year ago, and Sun Microsystems Inc in April last year.

Microsoft’s settlement with RealNetworks prompted Greve to maintain that the FSFE would continue to be a thorn in Microsoft’s side. FSFE will not stop defending everyone’s freedom in our digital society, in addition we are not for sale, he said at the time.

FSFE is already involved in the main EC antitrust case against Microsoft, which saw the company hit with a record 497.2m euro ($613m) fine and other remedies in March 2004.

As well as appealing the remedies in general, Microsoft in September launched an appeal against the interoperability sanction in particular, in an attempt to expedite a decision on whether it will be forced to share communications source code with open source software vendors.

Microsoft believes that software developed by users of the company’s published interoperability information should not be able to license their software under an open source license, while European Competition Commissioner, Neelie Kroes is determined to enable open source software developers to take advantage of the remedy.

I remain determined to ensure that all elements of the decision are properly implemented. This includes the ability for developers of open source software to take advantage of the remedy, said Kroes in June.

FSFE’s lawyer, Carlo Piana, told Computer Business Review that if its leave to intervene is granted then the free software group would once again assist the EC in providing industry and open source-specific information, but denied that the EC’s case is weakened by a lack of high-profile vendor supporters.

The Commission has enough legal expertise, but of course we will have a level of co-operation, and have in the past, providing input on the interoperability phase, he said. I expect others to join us in this case.

One potential intervener would be ECIS, the European Committee for Interoperable Systems, which was formed by IBM Corp, Oracle Corp, Nokia Corp, Real Networks Inc, and Red Hat Inc in April to provide assistance to the European Commission and is already involved in the wider antitrust appeal.