I am trying to extend the functionality of another plugin. I need to get data from it into an array to use in a different manner than the original plugin. (In this case, WPMUDev Categories and Listings plugins). Is there something in the Codex? How can I create a plugin that can use another plugins functions? Can I extend them and construct the parent nodes functions? I am not sure if these plugins are using classes or just straight functions.
I am just trying to get data from the plugin into a sidebar widget (in a form option element), but eventually I will be using this for the content area as well by using custom shortcodes. For now I just need a place to get started.