If you had a game where you wanted to send level states by e-mail, there would need to be a system function for that kind of program .
(folder) would be a table of (file)s where file(s) could be read in (at least at first) as strings (and maybe later 8bit clean etc.). Possibly the (folder) table would contain hints of the type of file.
The Codea app would only respond to .codeafile. Even if an app was made using the future open source engine, file triggers give the user a choice of which app the file should initiated each time a file is touched.
Could this be used to send code? Well, ya, but the implementation would be pretty indirect. At the present time you can create tabs from code and it would be doubtful that a tab create feature would be implemented. At best it would move repetitive copy and paste of code tabs as a start/copy/stop/new tab/paste/repeat process.
I don’t think it has to be identified to apple as a code sharing mechanism since that is not really the intent.