Welcome Tattersall!
I thought GS was only needed to open EPS files, on Windows. I was about to provide a link to those instructions, until I realized the problem is on a Mac.
Can I infer that something has changed in recent versions of Inkscape, (or maybe Mac and/or Linux?) to require Mac and/or Linux users to also install GS? If so, maybe we should put instructions for EPS / GS for Mac, or even Linux, in the FAQ?
Or could it be that installing GS is not the correct solution for opening EPS files on Macs?
Tattersall, are you unable to open any EPS files? Or is the problem with just one file? If just one file, I'm thinking the problem might be in the file, rather than your system.