On the Freebies page you can find useful free topic map utilities. The collection is small at the moment, but we hope that it will grow with time.
tmproc is an open source Python topic map engine, developed by Ontopian Geir Ove Grønmo.
TM4J is an open source Java topic map engine, developed by Ontopian Kal Ahmed.
The ISO 13250 compliant DTD supported by our topic map engine. (Note: The Engine also supports the XTM DTD.)
A zipped file containing some introductory materials to help you getting started with topic maps.