As of the summer of 2009, there is a small, 12 person, core team of developers. Within six months, we hope to open the development to a wider team of developers. So, if you want to get involved, please post an inquiry at the OpenMx developers' section of the OpenSEM forum.
OpenMx is licensed under the liberal open source Apache License, Version 2.0.
Software developers can find much more information about the OpenMx project at the OpenMx Developer Forums.