Civ4 World Template Builder is a C# GUI app intended to make it easy to create the basic layout for a Civilization IV scenario. It is not a map editor, nor a replacement for the built-in world builder. It does, however, give the ability to quickly create a map that can be imported into those tools for polishing.
The project is just getting underway, and the code should be considered alpha at this point. It is not yet feature complete, and only provides one world builder (albeit a useful one).
Even this web page is woefully inadequate; but at least it is a start. More to come.