OS X program to view .xif file
The general image opening magic I would try:


ImageMagick (installed via brew)
GIMP
XNView This explicitly lists it as possible: http://www.xnview.com/old/en/formats.html
GraphicConverter    


ImageMagick and GIMP are free GNU software. XNView is free too.

GraphicConverter is not free, not too expensive either, but can handle just about any image format to have been near a Mac in the last 20 years or so. It has a free trial.