Ωnyx is a free software environment for creating and estimating structural equation models (SEM). It provides a graphical user interface that facilitates an intuitive creation of models, and a powerful back end for performing maximum likelihood estimation of parameters. Path diagrams in Ωnyx can be exported to OpenMx, lavaan, and Mplus to allow an easy transition to script-based SEM software. Also, OpenMx scripts can be transformed into a path diagrams in Ωnyx.
Ωnyx is free software (as in free beer).