Anyone who thought Microsoft's settlement with long-time rival Sun Microsystems seemed surreal were in for another shock yesterday, when the software giant made some of its source code freely available on the Internet.

Microsoft released the code for WiX - a tool for building Windows installation packages from XML source code - on SourceForge.net, a site that provides free hosting for open-source software development projects. Software that does the same as WiX is already available for free, so the world won't turn upside down, but Microsoft reckons its version is better.

WiX is being offered under the Common Public Licence (CPL), an open-source licence originally authored by IBM, said Jason Matusow, Microsoft's manager of shared source initiatives. The licence, one of many approved by the Open Source Initiative (OSI) and listed on its opensource.org website, allows developers to modify the code and use it in commercial products, he said.

"It's the first time we have posted a project under an open-source licence, meaning one that is approved by the Opensource.org folks," Matusow said.

The move doesn't reflect an about-face on open source, he argued. Microsoft for years has been making source code available under various "shared source" licenses, all of which Microsoft wrote, he said. Those run the gamut from "reference-only" licenses that only let users look at the code to ones that allow modification and commercial release of code. The company will continue to release code under various licenses, he said. It might do so again under CPL, but has no plans to use the GNU General Public License, the license under which Linux is distributed and one that Microsoft has frequently criticized.

"We feel that the GPL presents certain challenges as a commercial software business," Matusow said. For WiX, the company decided CPL would be the best licence, he said. It chose to put the code on SourceForge because the site is widely used: More than 25 percent of the projects on SourceForge are Windows projects, he said.

This type of tool, a small piece of code with only a command-line interface, is used by a broad range of developers and is available as free software from other entities already. The tool creates a database that installer software can use to understand where best to place parts an application on a Windows PC, Matusow said. Microsoft believes WiX is better than the free tools and decided to offer it to developers, he said. It was developed at Microsoft and is already being used by several groups in the company, he added. WiX runs on Windows NT and Windows 2000.

"Someone can build a business on top of this code if they wish, and that is completely allowed by the licence," Matusow said. WiX can be downloaded from http://www.sourceforge.net/projects/wix/.