I wrote the extension for Udacity before they offered downloads. I agree that it is pretty useless now. I should see if it even works still, thanks for reminding me :) I should probably put a note to that effect in the readme.

I wrote this thing in one evening because I prefer to watch these videos on a big screen. What surprised me was how popular this quick hack became. There were people using it to download videos and share them with others in countries that blocked YouTube. I think at its peak there were a few thousand installs.