Recent changes are recorded in the publicly available repository:
http://github.com/stepcode/stepcode

This repo was moved and renamed in May 2012. Previously, it was at
http://github.com/mpictor/StepClassLibrary

Some are duplicates of changes recorded in the BRL-CAD repo:
http://brlcad.svn.sourceforge.net/viewvc/brlcad/brlcad/trunk/src/other/step/?view=log

Pre-BRL-CAD changes:
************************************************************************
 Updates from http://www.statik.tu-cottbus.de/fileadmin/project_dth/scl/
            Jan 2005 - Mar 2006
************************************************************************
 STEP Class Library Release 3.2 February 1998
************************************************************************
 STEP Class Library Release 3.1 October 1997
************************************************************************
 STEP Class Library and Data Probe release 2.1 June 1995
************************************************************************