That's an interesting video. Office has developed an incredible toolset for OS independent development and also very powerful UI libraries. I always wonder how Windows desktop development could look if they had released office components as libraries for developers. I think Windows development went downhill when office introduced the ribbon and started to deviate from the standard look and feel of the OS.
Office is C++, with 85-95% code shared between Windows, OS X, Android, iOS and Web; with a very tiny presentation layer on top.
Source: https://www.youtube.com/watch?v=zFmByeQ_ulo