Open source software, such as the popular Linux operating system kernel, typically allows users to modify the underlying code to suit their own needs, and to re-distribute the altered software, as long as the changes are made available freely to the development community.
Microsoft, which has compared some open-source licences 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 new Shared Source License, on Friday. It is available on the company's Web site and the code can be accessed through an evaluation or full version of the Platform Builder development tool.