This is a new one, and about as close as M$ has ever come to open-source I think. In a new move, Microsoft has announced that it will be licensing the user interface for MS Office 2007. This means as a developer (developing an non-competing product) you could use the MS ribbon idiom in you application as long as you comply with some style restrictions imposed by the license. This is interesting as many of the MS UI paradigms were aped by a number of applications, thus giving the UI more eyeballs and making M$ applications seemingly intuitive. With a big shift in paradigm from M$'s end they do feel that users will find it difficult to adapt to the new UI, so this is probably a way to evangelize the new UI. That's my reading of this announcement.
I personally have not used the ribbon interface yet, so I can't comment on the merits and demerits yet, but maybe some of you can...
