Im afraid of this app

There are only a few ways this app can work, and most of these mechanisms have tremendous privacy and security issues. Does this app install a proxy so that Safari now routes every page I view through the developers servers? Does the app install some JavaScript or CSS into some kind of Safari user template? Until the developer explains how the thing works, and I am satisfied this isnt click-tracking and key-logging, I plan to avoid it like the plague.

NSReviewWithPrompt about Tap Dictionary - In browser definitions