The Kivi's Underworld SDK is now available.  The purpose of the SDK is to make mods for Kivi's Underworld easier to create.  This SDK contains a bunch of documentation, 4 example mods, and a few tools.  The tools only work in Windows though. 

The example mods are an adventure, a playable class, a monster, and a powerup.  None of them are anything fancy, but they should help people get started.

Kivi SDK