Jaxe is a free open-source XML editor written in Java. It is adapted to structured narrative documents, and is easy to configure for a given XML language (both with specific menus to insert elements, and with Swing components associated with elements).
Typical Applications: Creation of language-specific editors.
Availability: multi-platform (has been tested on MacOS X, Linux and Windows with Java 1.3 and Java 1.4).
download from sourceforge
GPL licence