Sasha Philippov has announced the release of a free command-line tool for DocBook to SCORM 2004 conversion. It is the command-line Ant-based java application intended to generate SCORM 2004 compliant packages from DocBook 4.4 sources. It's free to use but not open source. It uses XSL stylesheets from DocBook project on SourceForge to generate HTML resources.
You can find more information on the tool at: http://pyxx.org/DocBook2SCORM/overview.html
Michael Smith reported an "Unsupported major.minor version 49.0" error with Java 1.4.2, so you may want to use the latest version of Java.
I am also doing some work with clients on authoring eLearning content in DocBook and exporting to SCORM, so I will definitely be giving this a try! Will post my results later...
Update: Sasha has recompiled the converter to support JRE 1.3 and higher.