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Microsoft’s copyrights in this specification are licensed under the Creative Commons Attribution-ShareAlike License (version 2.5). To view a copy of this license, please visit http://creativecommons.org/licenses/by-sa/2.5/. As to software implementations, Microsoft is not aware of any patent claims it owns or controls that would be necessarily infringed by a software implementation that conforms to the specification’s extensions. If Microsoft later becomes aware of any such necessary patent claims, Microsoft also agrees to offer a royalty-free patent license on reasonable and non-discriminatory terms and conditions to any such patent claims for the purpose of publishing and consuming the extensions set out in the specification.
Dean Hachamovich has some comments here.
Oh, and those who were wondering whether XML support in Office 12 will be a big deal can now put their skepticism to rest. Yes, this will have huge implications for Office 12, and I think you can safely assume that the ability to create and consume RSS will be a big part of the next version of Office.