Microsoft is making a transition from being a company that values only proprietary software to one that recognizes that developers produce much unpatented, freely available open source code on Windows machines.

That doesn't mean Microsoft is an open source code company, but it does mean the hostility it has previously expressed is abating, said Sam Ramji, director of Microsoft's open source labs, during the keynote address of the second day of EclipseCon 2008, a meeting of users of the open source Eclipse programmers workbench. Ramji's labs ensure that key open source code can work with Windows technologies.

There had been speculation that Microsoft might join the Eclipse Foundation or move its Java-like C# language onto the Eclipse open source programmer's workbench, once it became know that Ramji had accepted a keynote slot at the annual user group meeting. But no such dramatic move was forthcoming.

"We want to be the best platform for developing open source applications," Ramji said at one point. "We're seeing a lot of open source software written on top of Windows. It's a huge, sustainable market opportunity being the infrastructure of open source developers," he said at another.

Microsoft had its eyes opened when former JBoss CEO Marc Fleury told the company that JBoss business analysis indicated 50% of its customers were running its Java application server and middleware on Windows servers. Several years ago, Microsoft set up a working relationship with JBoss, while it was still an independent company, and improved JBoss performance on Windows by supplying better drivers. JBoss was acquired by Linux distributor Red Hat in April 2006.

Still, at moments Ramji seemed less intent on bringing an olive branch directly from Redmond than reporting on developments evident to anyone watching his company. "You're seeing a change in the company culture when Steve Ballmer at Windows Server 2008 talks about how good it is to have PHP applications running on Windows," he said. PHP is an open source scripting language backed by Zend Technologies that is used in many Web applications.