UPDATE: I unpacked the gif viewer file. It has a copy of the Windows XP Picture and Fax Viewer dll and instructions to view .gif files using it. The dll is the same as the one on my XP SP2 system. So basically, it's just using the XP viewer for .gifs. I also ran a MalwareBytes scan with the latest definitions and it came up clean - of course that's just scanning the uninstalled file. In summary, I'm pretty sure this is safe - that is, I'd use it but again, use your own judgement.

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken