GPS2Aperture Lite is a free and simple geotagging application for use with Apple's Aperture and Google Earth. You can view GPS positions of images in Google Earth, and embed GPS positions in the Master file for a Version.

GPS2Aperture does make changes to your Master files to embed the GPS data, but it does so using EXIFTool, the same command line application that is the basis of HoudahGeo and several other popular geotagging programs.