Open-source software, such as the popular Linux operating system kernel, typically allows people to modify the underlying code to suit their own needs and to redistribute the altered software, as long as the changes are made available freely to the development community.
Microsoft, which has compared some open-source licenses, particularly the GNU General Public License, to a "cancer," is championing its own "Shared Source License." This allows developers to change its source code but not to distribute the altered code for commercial purposes.
But some developers are concerned that downloading the shared-source code could lead to legal complications. They fear that Microsoft could accuse open-source developers of copying Windows code for their own projects, and could use the fact that they downloaded shared code as evidence.
Microsoft released the code, with the Shared Source License, on Friday. It is available on the company's Web site and can be accessed through an evaluation or full version of the Platform Builder development tool.
The move, on the eve of the O'Reilly Open-Source Convention, continues Microsoft's love-hate relationship with open-source software. The company has been attacking the GPL while acknowledging some of the powers of the open-source movement, such as the spirit of cooperation.
There are strings attached to sampling the Windows CE source code, though. In addition to the prohibition on using or distributing modified versions of Windows CE for commercial purposes, people must sign up for Microsoft's Passport service before getting access. Passport, an authentication system that can keep track of personal information, is used for Microsoft's programmer resource site and instant-messenger software as well as for its MSN service.
Microsoft gave a host of chipmakers early access to the source code for the next version of Windows CE, code-named Talisker. The chipmakers may optimize the software for their chips but won't have broad access to add features or make other changes to the software.
Since earlier this year, Microsoft has been touting the fact that it has been sharing more of its code.
Staff writer Matthew Broersma reported from London. News.com's Stephen Shankland and Ian Fried contributed to this report from San Francisco.