Free software is great, and corporate America loves it. It's often high-quality stuff that can be downloaded free off the Internet and then copied at will. It's versatile - it can be customized to perform almost any large-scale computing task - and it's blessedly crash-resistant. A broad community of developers, from individuals to large companies like IBM, is constantly working to improve it and introduce new features.  But now there's a shadow hanging over Linux and other free software, and it's being cast by Microsoft. The Redmond behemoth asserts that one reason free software is of such high quality is that it violates more than 200 of Microsoft's patents. And as a mature company facing unfavorable market trends and fearsome competitors like Google , Microsoft is pulling no punches: It wants royalties. If the company gets its way, free software won't be free anymore. The conflict pits Microsoft and its dogged CEO, Steve Ballmer, against the "free world" - people who believe software is pure knowledge.