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.