The need for this plugin has largely been superceded by the creation of the (official) ACF "Clone" Field. Therefore what little maintenance I was doing (and that was very little..) for this plugin will end.
This is a plugin which adds a Reusable Field Group type to the Advanced Custom Fields WordPress Plugins. This allows you to create a group of fields once, and reuse it within any other field group.
This plugins was created using the Advanced Custom Fields field type template repository. As such, there is a bunch of boilerplate code that is not currently used.
For more information about that process a new field type, please read this article.