Microsoft’s Silverlight 2, the latest plank in the company’s rich Internet applications development platform, makes its formal debut Tuesday.

Although Silverlight is only a year old, Microsoft claims one in four consumers has access to a computer with Silverlight on it.

It says penetration in some countries approaches 50% and that its ecosystem includes 150 partners and “tens of thousands of applications.”

Of course virtually every computer in the world has Adobe’s rival, Flash, on it but Silverlight 2 is supposed to shorten Flash’s lead – Microsoft is even contemplating getting it on iPhone someday should Apple ever smile on browser plug-ins, which would be a real poke in the eye for Flash. Steve Jobs doesn’t like Flash.

During the Summer Olympics NBCOlympics.com was powered by Silverlight and had more than 50 million unique visitors, 1.3 billion page views, 70 million video streams and 600 million minutes of video watched, increasing the average time on the site from three minutes to 27 minutes.

CBS College Sports, Blockbuster, Hard Rock Cafe International, Yahoo! Japan, AOL, Toyota and HSN are building their next-generation experiences using Silverlight.

Since Silverlight is supposed to be cross-platform – and support Mac, Windows and Linux via Firefox, Safari, IE, even Chrome – Microsoft said it’s funding Silverlight-Eclipse integration and providing new developer controls of the Silverlight Control Pack (SCP) under the Microsoft Permissive License.

Microsoft is paying for Soyatec, a two-year-old Paris-based open source outfit with XAML Java-.NET interoperability skills and a member in good standing in Eclipse, to lead a project to integrate Silverlight into the Eclipse IDE.

Soyatec is supposed to release the project as a set of plug-ins under the Eclipse Public License 1.0 on SourceForge and has submitted it to the Eclipse Foundation as an open Eclipse project.

There should be a preview at http://www.eclipse4sl.org on Tuesday. The complete version won’t be available until the second half of 2009.

Microsoft is also supposed to release a Silverlight Control Pack and publish the technical spec for the Silverlight Extensible Application Markup Language (XAML) vocabulary on MSDN.

The SCP, which will augment the built-in control set in Silverlight, will be released under Microsoft’s Permissive License, an Open Source Initiative-approved license, and include controls such as DockPanel, ViewBox, TreeView, Accordion and AutoComplete.

The Silverlight XAML vocabulary spec, released under the Open Specification Promise (OSP), is supposed to make it easier for third-party ISVs to create products that can read and write XAML for Silverlight.

Miguel de Icaza, the head of the open source Moonlight project, reassuringly says that “the Silverlight Control Pack under the Microsoft Permissive License really addresses the needs of developers by enabling them to learn how advanced controls are authored directly from the high-quality Microsoft implementation. By using the OSP for the Silverlight vocabulary, they further solidify their commitment to interoperability. I am impressed with the progress Microsoft continues to make, and we are extremely satisfied with the support for Moonlight and the open source community.”

Moonlight lets Silverlight apps run on Linux and provides a Linux software development kit (SDK) for building Silverlight applications.

Otherwise, Silverlight 2 supports Visual Web Developer 2008 Express Edition, a free download.

It also includes several new rich controls such as data grids and advanced skinning capabilities, as well as support for the .NET Framework, REST, WS*/SOAP, POX, RSS and standard HTTP services and programming languages such as Visual Basic, C#, JavaScript, IronPython and IronRuby.

The widgetry includes Silverlight DRM, powered by PlayReady, improved server scalability and expanded advertiser support.

Starting Tuesday see http://www.microsoft.com/silverlight to download Silverlight 2.