Microsoft has made one of its most direct overtures to the open-source software community to date, in the form of an invitation to Michael Tiemann, president of the Open Source Initiative (OSI), to begin a "productive conversation".

Tiemann, who is also vice president for open-source affairs at Linux distributor Red Hat, said Microsoft had contacted him as president of OSI in order to open up a top-level dialogue, according to a report in industry journal eWeek. He said the OSI would take the offer at face value, according to the report. Tiemann has exchanged emails with the company but has not yet met anyone. Tiemann would be most likely to meet with Brad Smith, Microsoft's general counsel, who has been involved in attempting to ease relations with the open source world.

Red Hat could not immediately confirm the report.

The move represents part of Microsoft's latest effort in dealing with the growing popularity of open-source or "free" software, which makes source code available to anyone and isn't controlled by any single company. Linux is Microsoft's particular nemesis, because it threatens the company's lucrative Windows operating system monopoly, with other potential threats including the widely used Apache Web server and open-source projects providing networking interoperability, productivity tools, databases and the like.

In case there is any ambiguity about Microsoft's stance with regard to open source, the company's filings with financial regulators cite the development model as a threat to Microsoft's businesses in servers, clients, productivity software and even handheld computers, as well as posing a challenge to the company's general business.

The company has tested various tactics in dealing with open source in general and Linux in particular, characterising Linux's licence as a "cancer", arguing that open source doesn't guarantee interoperability and that Linux should be distinguished from open source.

"Get the facts", an advertising effort launched in 2003 draws on research from third parties to show that Windows is more secure, reliable and cost-effective than Linux.

Such efforts led Stanford law professor Lawrence Lessig in April to claim that Microsoft is preparing "an all-out war" on the open source community, specifically Linux.

At the same time, Microsoft has begun portraying itself as more open to "free software" ideas, publishing some tools under open-source licences and allowing some organisations to inspect its source code under the company's "shared source" programme. The company has begun regularly maintaining a presence at open-source events and Microsoft CEO Steve Ballmer reportedly met with Red Hat CEO Matt Szulik earlier this year, although Red Hat has never confirmed the meeting.

Microsoft is not the only proprietary software company to have an uneasy relationship with open source and Linux, although its stance is among the most extreme. Sun Microsystems, for example, has begun selling Linux and is in the process of making its Solaris operating system open source, but continues to disparage some of the core aspects of the open-source development model.

In April, Sun president Jonathan Schwartz justified the company's open-source strategy with an attack on the GPL (GNU General Public Licence), which covers Linux, Samba and other prominent open source projects. He characterised the GPL as a tool allowing United States businesses to pillage developing countries of their intellectual property.