Why can't you buy Papers from the Mac App Store

One of the main reasons why we can't have Papers in the Mac App store is that Magic Citations cannot be implemented without violating some of the rules of the Mac App Store, the major issue being the requirement to sandbox the process. In particular, Magic Citations needs to determine the front application, and makes use of Applescript to interact with the front application. It also needs read access to the file corresponding to the front window, as well as write access to that file (in the case of Word), or to a newly created file in the same directory.