iConquer Plug-in Kit for Mac

From KavaSoft:

iConquer allows you to create plug-ins for both player personalities and maps. Use your artificial intelligence hacking ability to make the next great player algorithm. Or use your artistic talents to make stunning Aqua-licious game maps.

To create player plug-ins, you'll need a basic understanding of developing Cocoa software for Mac OS X in Objective-C. If you're familiar with Java, you may just need to read through the Objective-C tutorial.

To create map plug-ins, you'll need a graphics program that can create TIFF images with transparency, such as Adobe Photoshop.

For more information on iConquer, see:
http://www.kavasoft.com/iConquer/