GNU social by Jonas Laugs with lettering by Steven DuBois. 
License: CC0 1.0 Universal http://creativecommons.org/publicdomain/zero/1.0/

Default avatars are modified from an image by Francesco 'Architetto' Rollandin.
http://www.openclipart.org/detail/34957

Some icons by Mark James
http://www.famfamfam.com/lab/icons/silk/
http://creativecommons.org/licenses/by/2.5/ Creative Commons Attribution 2.5 License