List of OSS or free STEP programs
Express Schemas
SC4 Express Archive - for STEP AP schemas that are International Standards (IS)
STEPmod on Sourceforge - for versions of modular STEP AP schemas that are in development
CAX-IF Schemas, Recommended Practices, and Test Rounds - for AP203, AP214, and AP242
Other open source projects related to STEP and/or EXPRESS
Express Engine - used to validate models with schemas. Old website is here
JSDAI, similar to STEPcode but written in Java. Created by LKSoftWare GmbH.
Express for Free, also here
SEBNF2Pars - Creates Part 21 parsers from an EBNF representation
lgtstep - a Logtalk STEP implementation
Scripting Applications for STEP Part 21 files - uses Prolog
http://github.com/mvaerle/python-ifc
http://www.ifcgears.com/extender.php
Free, closed-source programs related to STEP / EXPRESS
expfront - free on-line EXPRESS schema checker
IDA-STEP Viewer - free downloadable STEP file viewer
Jen-X p28 schema generator and p21-p28 mediators - for shipbuilding STEP AP’s