BlueCurls KDM4 theme. Based on on "Glassified KDM" theme.
To install, copy the folder BlueCurls/ to /usr/share/apps/kdm/themes/BlueCurls/. Select the theme "BlueCurls" in System Settings > Advanced > System > Login Manager. (For Linux distros other than Gentoo, the file ./kdm/BlueCurls/BlueCurls.xml can be edited to change the header.)
Also see BlueCurls wallpaper, grub screen, fbcondecor(gensplash) and ksplash.