I suggest this strategy because I've witnessed IBM using it with great success. In the WebSphere division, we contribute to countless open source projects, including the Apache HTTPD, Dojo Toolkit, and Eclipse Equinox projects. We then utilize code from these projects with IBM enhancements inside of WebSphere Application Server. This strategy allows us to do more with less.
I hope friends at RIM can learn a lesson from IBM's use of open source for competitive differentiation. With Dion and Ben at Palm, you can bet that Palm is thinking about using open source more effectively within its strategy.
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p.s.: I should state: "The postings on this site are my own and don't necessarily represent IBM's positions, strategies, or opinions."