Well... there are three things to consider:
1. there is a ribbon implementation available somewhere in the internet but you may have to search for it
2. you can implement a ribbon-like widget using a dock widget
3. there are licensing issues when using a ribbon. Microsoft has some patent for using it in "office-like" applications or something so it's easy to fall of a cliff as most applications can be considered "office-like".

There is also the "ribbon sucks" argument, but that's subjective...