EWeek had an interesting interview with Steve Ballmer that covered Microsoft's view of open source along with other topics after the Microsoft Worldwide Partner Conference. http://www.eweek.com/c/a/Enterprise-Apps/Microsofts-Ballmer-Opens-Up-to-Partners/?sp=0&kc=EWKNLLIN071508STR3. Although Ballmer denies that Microsoft will be "open sourcing" any of its core products, he emphasizes that Microsoft wants to encourage opens source development on its platform (see below):
However Microsoft will support and interoperate with open-source software in various ways, Ballmer said. "Will we interoperate with products that come from like Linux, from the open-source world? Yes, we will," he said. "Will we encourage people who want to do open-source development to do it on top of Windows? Yes, we're proud that the best PHP system in the world is actually the one that runs on Windows today, not the one that runs on Linux.
"So we're going to encourage open-source innovation on our platforms, and around our platforms. And, you know, we see interesting things where bits and pieces of technology, commercial companies are now starting to provide it in an open-source form or to digest in an open-source form. And we're open to that as well. But our fundamental business model will remain kind of commercial software, advertising, enterprise licensing, etc."
As this interview indicates, Microsoft is continuing to move towards engagement rather than confrontation with the open source community. However, remember that Microsoft is a big organization with a very strong culture to which these changes are very difficult. This change will take time and we should expect relapses in their engagement with the open source community. And this change should not be mistaken for adoption of the open source philosophy, rather it is a recognition of reality. Microsoft recognized that the world has changed and they need to deal with the world as it is, not as they wish it to be.
This change does provide an opportunity for open source companies.