Today we announced a new licensing program for the Microsoft Office 2007 user interface components. Licensing UI in this way is something for new Microsoft, but it should work out well for developers who want to take advantage of all the research that went into the UI to improve the usability of their own applications (or who just want to make sure their apps look/behave like Office).
The license is short and simple (and royalty-free!), and it's accompanied by a detailed set of design guidelines that explain the finer details of implementing the UI controls in the same way as Office. So you get all the tips you need on how to behave consistently with Office, plus a license that gives positive assurance that you have the right to use the UI in your app. You can read more details here and on Jensen's blog, and watch us discussing the license on Channel 9.
I've been helping the Office team think through this licensing approach for a good long while now, and I think they came up with a great solution.