Apps for the iPhone, iPad, and iPod Touch are stored in a file with the "IPA" (iPhone App) extension. As seen on the Wikipedia page for ".ipa_(file_extension)". It says: "Files with the .ipa extension can be uncompressed by changing the extension to .zip and unzipping."
The name of your Mooncraft or Lunacraft file will depend on what version you currently have. Update 1.7.0 is called "mooncraft 1.7.0.ipa". Update 1.8 is called "lunacraft 1.8.0.ipa". Update 1.9 is called "lunacraft 1.9.ipa". Here we'll assume you have version 1.9.
- Find the file called "lunacraft 1.9.ipa". On a Mac in is in "(your home directory)/Music/iTunes/Mobile Applications".
- Copy that file somewhere and change the extension to "zip", so it's called "lunacraft 1.9.zip"
- Un-ZIP it. You'll get a folder called "lunacraft 1.9".
- Within this should be files called "iTunesArtwork" and "iTunesMetadata.plist", and a folder called "Payload".
- Look in the "Payload" folder. This should contain another folder called "lunacraft.app".
- Look inside this folder. You should see lots of files, including "items.txt", "itemscan.txt", and "recipes.txt".
The contents of these files does not necessarily reflect the actual functioning of the game. (The game designers might have added new information in some other file, and the TXT files are just a relic from older versions). However, everything the contributors to this Wikia have found so far (as of October 2012) seems to agree with the items.txt and other files.