The olive branch - well, okay, twig - olive twig - that Microsoft extended to the open source Eclipse Foundation Wednesday was the undertaking to help make the Eclipse Standard Widget Toolkit (SWT) work with Windows Presentation Foundation (WPF) so it's easier for Java developers to write programs that look and feel like native Vista apps - almost as if they were written in C#.

Eclipse is porting SWT, its platform portability library, to WPF, and now Microsoft will be involved.

And on the identity front there are moves afoot to link Eclipse's Higgins project with Microsoft's Cardspace widgetry. Microsoft has been providing protocol information for interoperability.

The announcement, as expected, was made during a keynote given at EclipseCon by the director of Microsoft's Open Source Software Lab Sam Ramji, who said Microsoft gets "the same revenue from an open source application as we do from a closed source application: zero dollars. When SAP ships software on Windows, they don't send us any money for the SAP license. Our entire opportunity is in platforms. We make money by being a better platform to run applications on. We're the layer underneath. We're the batteries included."

So Microsoft is now investing in open source, he said, to be the best platform for developing open source programs on, the "infrastructure of open source developers."

There are supposed to be further conversations between Microsoft and Eclipse about further détente like maybe a C# IDE and accepting Java as a first-class citizen on Windows.

Microsoft has not joined Eclipse and will not delegate Eclipse committers to Eclipse projects.

Cisco, by the way, has joined Eclipse, intending to support Tigerstripe, the development of a software tool that enables telecom companies to create models of next-generation networks, the basis of management applications.