The Galaxia Workflow Engine has been retired from Tiki4 and is superseded by Category Transitions, which serves the same purpose, but much more tightly integrated.

For more information about why, please see:

Galaxia was a open source activity-based Workflow engine integrated in Tiki which was based on Openflow.

To be clear, Galaxia is a dead project and sites/pages are only kept for posterity. There is no Galaxia code in Tiki since Tiki4 (although it will live forever in SVN on SourceForge).