Microsoft and open-source backers: best 'frenemies' forever?

Ballmer's statement -- along with follow-up claims by Microsoft executives that they had found violations of 235 patents in Linux and other open-source software -- caused a sudden refrosting of what had been a slowly thawing relationship between the company and the open-source community.

Over the past several years, Microsoft -- whose combative CEO once called Linux a "cancer" from an intellectual property standpoint -- has set up its own open-source testing lab, begun hosting open-source projects for free on its CodePlex Web site and signed partnership deals with open-source vendors such as Red Hat Inc.'s JBoss Inc. division, MySQL AB, SugarCRM Inc., XenSource Inc. and Zend Technologies Inc.