When the ribbon was introduced, Microsoft asserted patent rights and asked for a license in order to use it. In fact, you were not allowed to use ribbons in your app without a license.
Since then, license text has mostly disappeared from Microsoft's site. The license page no longer exists. You can't apply for one. I personally last saw text referring to a license requirement in the ribbon MFC samples distributed with Visual Studio. But the question if Microsoft requires a license or asserts patent rights seems to still be open - there has been no statement from Microsoft, and a quick google shows lots of people asking the same question.
The impression I have is that Microsoft let the patent expire at the basic 7 year mark (~2014) as they deemed their UX R&D investment had given them enough lead over competitors in the Office suite space (the primary applications that required a paid license and were not allowed the free license). Around that time Microsoft added Ribbons to Win32 and WPF as freely available controls with no additional license. Fluent Design also seems working to add Ribbon controls to all UI control toolkits with no mention of licensing or patent rights (and seems to be working to move even Office to shared controls).
I'm pretty sure Autodesk use a licensed forum of MS ribbons in a lot of their software; AutoCAD, Inventor etc. But I can't find any references to the specific license agreement...
You can read about that here: https://web.archive.org/web/20100719112606/http://blogs.msdn...
Since then, license text has mostly disappeared from Microsoft's site. The license page no longer exists. You can't apply for one. I personally last saw text referring to a license requirement in the ribbon MFC samples distributed with Visual Studio. But the question if Microsoft requires a license or asserts patent rights seems to still be open - there has been no statement from Microsoft, and a quick google shows lots of people asking the same question.
* https://office-watch.com/2018/can-microsoft-office-ribbon-us...
* https://stackoverflow.com/questions/563312/is-the-ms-ribbon-...
* https://www.infoq.com/news/2018/02/Ribbon-UI/
* and me: https://news.ycombinator.com/item?id=14095662