Interesting link. One of the core ideas behind Windows' success back in the day (when almost every program implemented its own unique GUI system and they were very inconsistent) was that it provided reusable UI components and Microsoft said that all developers
should use their standard design, GUI components, and keyboard shortcuts to provide consistent interfaces for Windows programs. Seems rather hostile that Microsoft would now be suing someone for doing exactly what they always told everyone to do (especially considering that other developers using their UIs is a significant part of what made Microsoft itself so successful).
I guess the fact that they made it available to anyone not directly competing with their office suite is something. But the whole "Do what I tell you to do!" "Ok, I will." "Now you're in trouble for doing that!" routine still seems obnoxious.