Hoping to boost the use of its Windows CE software in devices, Microsoft is announcing that it will share more of the operating system's source code and allow device makers to make changes to that code.

The announcement marks the first time that Microsoft will allow others to make changes to the operating system source code, compile the code for use in commercial products, and not have to share their changes with Microsoft or anybody else, said John Starkweather, a product manager at Microsoft.

Windows CE was developed for devices including consumer electronics, wireless routers, industrial controllers, handheld computers, set-top boxes, voice over IP phones and thin clients. It competes with proprietary operating systems as well as with versions of open source Linux designed for embedded use.

"The option to ship derivatives of Windows CE will give device makers another opportunity to innovate, thus we will see a further expansion of the types of devices that are powered by Windows CE," Starkweather said.

The expanded source licensing for Windows CE will come with Windows CE 5.0, scheduled to be released to manufacturing on 9 July. General availability should follow shortly thereafter.

More than 2.5m lines of code will be available for Windows CE 5.0, including the kernel, user interface, hardware drivers, and networking stack, Starkweather said. For Windows CE 4.2, Microsoft made about 2m lines of code available, which users were allowed to use only for reference and debugging purposes.

The expanded source code licensing with Windows CE 5.0 comes in addition to the Windows CE Shared Source Premium program that Microsoft launched last year. Under that program, licensees can get almost all of the CE source code and make modifications to it, but they are required to share their changes with Microsoft, Starkweather said.

Additionally, the Shared Source Premium program was limited to a small group of chip makers and device makers in a limited number of countries. With Windows CE 5.0, any licensee in any country will be able to access the source code, Starkweather said.

The Windows CE Shared Source Premium program will continue, and Microsoft may expand it to include some additional companies, Starkweather said.