Microsoft is licensing the new UI (user interface) in Office 2007 for free so developers can build applications that look similar to the programs in the suite.  Microsoft is licensing both design and functionality of Office 2007's Ribbon UI, as well as offering guidelines for implementing it.  Developers and ISVs (independent software vendors) can sign up with Microsoft on the Web and register products that will use the UI.  If you are interested, please contact your ISV Evangelist or click here for more information.