4th Edition - Version 4.0
From the introduction:
This document contains the complete Dungeons Daring rules system in an editable format and free for use under the terms of the Open Game License.
The document is the Open Game Contents (system reference document) for the Dungeons Daring Game Masters Guide (Version 4) game book.
The Open Game Content Reference Document is provided in ODT format, for LibreOffice Writer.