(adapted from: http://www.rumbud.com/d/how-to-install-gnumeric-and-other-linux-apps-on-mac-osx/)
Install homebrew
brew install gnumeric
Open the "Script editor" application and paste the following code:
tell application "Terminal"
do script "gnumeric &"
end tell
Save it as an application. Mouse over the launch icon you see here, hold control while clicking and select 'copy image'
Now right-click the applescript icon you created earlier. Select get info.
In the upper left corner of the window, you’ll see the applescript launch icon. Click it and hit Command-V