The following resources are available to help you get started developing.
The reference implementation for GEDCOM X is being developed in Java.
The GEDCOM X Java implementation is instrumented such that it generates a set of libraries that will allow you to produce and consume GEDCOM X on a variety of different platforms. The functionality of the generated libraries is limited to defining the base GEDCOM X data structures (classes, structs, etc.) and providing a way to serialize and deserialize the structures to/from XML or JSON.