Opens a window into the source.
Defenestration is an English word meaning, "throwing out of a window". This add-on will put into a window any source code of the element you are hovering over. That's it.
The source code is licensed under GPLv3, found at https://github.com/polypmer/fenestrate
The syntax highlighting is done with the 3rd party (BSD-3) library highlight js.