Footprints in Layout can use scripts and primitives in defining the geometry needed. Scripts can also move and/or create ports. Scripts can be written in any Windows supported languages. Universally supported languages include JavaScript and VBScript.
When Layout needs to retrieve footprint geometry, it invokes the script, passing an object called LayoutHost. This object provides the interface to the needed functions within Layout necessary for creating geometry and accessing information within Layout. The script then calls the member functions of this host object to define the footprint appropriate.
Documentation on scripting within Windows including language definition for JavaScript and VBScript can be found at: http://msdn.microsoft.com/scripting/.