Microsoft chairman Bill Gates has sent an email to customers claiming that his company is working to make software more interoperable, and simultaneously taking a swipe at open source software.

Gates pointed to Microsoft's work with XML as one step it is taking towards making systems work better together.

"Our goal is to harness all the power inherent in modern (and not so modern) business software, and enable them to work together so that the whole is greater than the sum of the parts," he said in the email.

"We want to further eliminate friction among heterogeneous architectures and applications without compromising their distinctive underlying capabilities."

Gates warned customers not to confuse open source with interoperable software. "Interoperability is about how different software systems work together. Open source is a methodology for licensing and/or developing software that may or may not be interoperable," he claimed.

"Additionally, the open source development approach encourages the creation of many permutations of the same type of software application, which could add implementation and testing overheads to interoperability efforts."

Gates added that Microsoft is involved in work that contributes to interoperability across the industry.

"We publish APIs, protocols and software development kits, and license our underlying intellectual property associated with this technology, to help others deliver interoperable software," said the email.

"And we collaborate and share technology with a wide array of industry participants, some of them direct competitors, to deliver interoperability solutions that work well with our products."

Microsoft has launched a website on interoperability which can be seen here.

A senior Microsoft executive took another swipe at Linux last week, suggesting that its reputation as a secure operating system is a myth.