GTK2/GTK3 theme, Xfwm4 theme and more
This theme is an all-grey variation of Greybird
, originally made by Simon Steinbeiß and Satyajit Sahoo and default theme in xubuntu.
As the original theme, Greybird-graphite is dual-licensed as GPLv2 or later and CC-BY-SA 3.0 or later.
if you want to follow the development take a look here