Viewing Blizzard's interface code
From Wowpedia
You can view Blizzard's FrameXML and AddOns code and artwork by instructing the WoW client to extract those files, or by viewing them online.
Extracting interface files
Since the switch to the streaming download system in patch 4.0.1, the previously-used Interface Toolkit is no longer supported by Blizzard. Instead, the interface data and artwork can be extracted directly from the client (as of patch 4.0.6) by using the following console commands to extract the code and art, respectively:
ExportInterfaceFiles code ExportInterfaceFiles art
Once extracted, the files can be found in the "BlizzardInterfaceCode" and "BlizzardInterfaceArt" folders in the World of Warcraft directory. For detailed instructions concerning access to the console, see Console.
Note: The ExportInterfaceFiles command only works from the actual console (accessed by starting WoW with the
-console flag, then pressing `, and not via a /console slash command) while on the login screen (and maybe the character selection screen). Once you're in the game, it no longer works and you will just get an "Unknown Command" response.Viewing interface data on the web
There are several ways to view the Blizzard interface code online