These are the graphics of the Cuyo level which, depending on difficulty settings, is named Balls at ease or Frightened balls or Angry balls.

The graphics are dual licensed under the GPLv2 and under the OINM license version 0 (see http://www.weyer-zuhause.de/mark/software/oinm_license_0).

The graphics were generated by programs and these programs constitute the source form of the graphics in the sense of the GPL and the OINM license. In short, distribution without the source is a license violation.

EDIT: I replaced the archive by a version with png instead of xpm format.