The icons are mostly derived work from other icons. As such they are
licensed accordingly to the original license:

Project                 License                   File
----------------------------------------------------------------------------
CP (Crystal Project)    LGPL                      image_LICENSE_CP.txt
Enthought               BSD 3-Clause              LICENSE.txt
GV (Gael Varoquaux)     Public Domain             N/A
Nuvola                  LGPL                      image_LICENSE_Nuvola.txt

Unless stated in this file, icons are the work of Enthought, and are
released under a 3 clause BSD license.

Files and original authors:
----------------------------------------------------------------------------
blockcanvas/block_display/images:
           bound_input_variable.png | Enthought
          bound_output_variable.png | Enthought
              function_variable.png | Nuvola
         unbound_input_variable.png | Enthought
        unbound_output_variable.png | Enthought

blockcanvas/canvas/images:
                     bluebullet.png | Nuvola
                 bluebulletover.png | Nuvola
            close_button_normal.png | GV
              close_button_over.png | GV
           expand_button_normal.png | Nuvola
            expand_button_ovrer.png | Nuvola
                     input_icon.png | CP
                    output_icon.png | CP

blockcanvas/function_tools/images:
              function_variable.png | Nuvola
             preferences_button.png | CP

blockcanvas/model/images:
              filter_expression.png | CP
                   filter_group.png | GV
