I've seen at least a bunch of non-MS apps that use the ribbon. Spoon Studio, a tool for containerizing Windows applications, is one that I used recently. There's more, but I can't come up with them.
I think it's a very powerful paradigm. Compared to LibreOffice's "toolbar overkill", it's surely a step forward. Making a large amount of operations in a simple way is always difficult, the ribbon seems a least-bad option compromise, that works quite well.
