I've just submitted v1.1.2 to the plugins for review. That version incorporates downward-compatible changes introduced in Zen Cart v1.5.5.

Please note that the base functionality of this plugin has been included in the Zen Cart core since v1.5.2. This plugin now extends that functionality, providing a method to insert Font Awesome glyphs into your CSS buttons. If you are running Zen Cart v1.5.2 or later, you'll need to install this plugin only if you want that additional functionality for your store.