This is a php 5 only API module, which allows modules to extend your objects. It basically helps you to implement the Facade pattern in a modular way. So as of now it allows you to:
- Extend an object by providing an Extender Class
- Extend an object simply by some functions, each implementing a method
- Override any dynamically added method by providing functions or an Extender Class
- Lazy load needed include files upon method invocation
So apart from "allowing modules to extend an object", this also allows one to:
- Easily lazy load huge parts of an objects implementation, invisible for the caller.
- Allow modules to dynamically alter an implementation by using overriding.
Hence such an Extended Object can also serve as a clean abstraction for module provided callbacks!
To see how it actually works have a look at the provided docs.
Update: It turned out that this approach doesn't work very well in PHP, such that there is no clean abstraction for callers. Without a clean abstraction modules have to deal with the increased complexity though. As a consequence the module is being discontinued.
If you are using Rules it is recommend to remove *this* module from your Drupal installation.