Q:

Ribbon interface for GTK and Qt

Is it possible to implement ribbon interface in Windows7 in GTK or Qt? If yes how to do it?

A:

Yes, some libraries for Ribbon widgets have already been released.

 see this post and this one. 
There is also QtitanRibbon, an implementation of Microsoft's Ribbon UI for QT.

A:

I don't have enough rep to vote or comment, but @Daniele Lupo's comment about needing to sign an agreement isn't quite true. There is enough prior art floating around that suggests Microsoft won't be awarded the patent.
Source: Ribbon (computing)

