The game software is now embedded in a package at
~/Library/Application Support/Steam/SteamApps/common/sid meier's civilization v/Civilization V.app
Once you get to this package you can Open Package and it looks like the one that comes from the App Store. So the MainMenu.lua file is at :
Civilization V.app/Contents/Home/assets/UI/FrontEnd/MainMenu.lua
However, I have confirmed that commenting the usual line in this file does not enable the mods menu item. I suspect more drastic surgery may have been done by Aspyr to prevent us from enabling mods on the Mac version.
~/Library/Application Support/Steam/SteamApps/common/sid meier's civilization v/Civilization V.app
Once you get to this package you can Open Package and it looks like the one that comes from the App Store. So the MainMenu.lua file is at :
Civilization V.app/Contents/Home/assets/UI/FrontEnd/MainMenu.lua
However, I have confirmed that commenting the usual line in this file does not enable the mods menu item. I suspect more drastic surgery may have been done by Aspyr to prevent us from enabling mods on the Mac version.