These images are licenced under a double CC-SA (Creative Commons
Attribution ShareAlike) and GPL licence (see file COPYING in that
directory). These licences are such that when combined with other
works the whole work should be under the GPL or CC-SA. So you cannot combine
the images with other materials, for example a manual text if the manual
text is under a licence that doesn't allows to be relicenced under the
conditions of the GPL or the CC-SA. For example a manual licenced under
the GFDL or the artlibre licence cannot be combined with the image.