DDL is broken down into several different packages for download. If you're after everything DDL related, then check out the SDK. Otherwise, the library source, utility source and utility executables are all available as separate downloads.
DDL Beta SDK
The Standard Development Kit contains all the source, documenation and scripts for DDL development.
In order to run the D scripts provided, simply run/compile them with Build.
DDL Beta Documentation
Doc generation is presently offline pending a complete overhaul of the doc generation system. This will be available closer to release.
DDL Beta Utilities
The DDL utilities package is a collection of programs designed to help programming with the DDL library. These are explained in more depth on the Utilities Page. The sourcecode for the utils is available via the SDK, above.