Hey! I'm working on that! This is just the core of the app. Expect a full GUI within the month.
I made this a CLI app for starters the following reasons...
1. there is a very limited number of OSX apps that are for working on NES ROMs (and other ROMs for that matter)
2. there are NO apps like this for *nix.
3. NAPIT (windows) is SLOW. I wanted my app to EAT it.
4. I thought up the terminal-based preview one night and thought that would be a snazzy feature.
5. It was faster for me to whip this up for simply extracting sprites.
There WILL be a full, OSX-native, Cocoa-based app in the near future. I'm just trying to complete the feature set of the CLI tool.
Also, it's bad form to badmouth the developer, I mean, HEY, it's FREE and it WORKS. If I was charging 30$ for this, bitch all you want, but until then, keep yer anger to yerself. ;)