All images in the 'static/homepage' area are free for use, some with attribution required, as given below:

This file lists the sources of some images:

CHART core icon:
  http://commons.wikimedia.org/wiki/File:Hastelloy_Monel_Inconel_Incolloy_Pipes_and_Tubes.jpg
  (Creative Commons)

CHART project icon:
  http://commons.wikimedia.org/wiki/File:PyramidOrbit.jpg
  (GNU Free Documentation and Creative Commons)

Conductor icon:
  http://www.wpclipart.com/music/performance/conductor/conductor_seated.png
  (public domain)

Robot image
https://openclipart.org/detail/20508/-by--20508