Microsoft Office Ribbon
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You mean, like, from a legal point of view? As far as I know Microsoft has tried patenting it and has run a few scare tactics with letting people sign "free" (as in beer) licenses. However, I don't think they have a (valid) patent.
"This thread":https://qt-project.org/forums/viewthread/19987 might be interesting for you.(I am not a lawyer, this is not legal advice bla bla bla yadda yadda, look at what our world has become)