Tux Paint: Open Source Drawing Software for Children

"Tux Paint" is a drawing program for young children.  It provides a 
simple interface and fixed canvas size, and provides access to previous 
images using a thumbnail browser (e.g., no access to the underlying 
file-system).  Unlike popular drawing programs like "The GIMP," it has 
a very limited tool-set. However, it provides a much simpler interface, 
and has entertaining, child-oriented additions such as sound effects.

This requires libpaper, and SDL_pango is an optional dependency.
