Maybe a cross between DownloadsII and
Links and Downloads Manager (perhaps using a modified short linkbit). Since all three of those sites have suspiciously similar domain names and similar yet aesthetically different download sections, it is probably custom coded, although the setup does look suspiciously like a downloads system I have used in the past. I currently use LDM, but I haven't been to our Downloads section recently so I'm not sure what I'm remembering.