Revisions allow you to track differences between multiple versions of your content, and revert back to older versions.
If you want to get involved, please post an inquiry at the OpenMx developers' section of the OpenSEM forum. If you are interested in building OpenMx from source, take a look at the OpenMx Compilation How-To Guide. We also have a some discussion about how we use GIT. The project is licensed under the Apache License, Version 2.0.
OpenMx is licensed under the open source Apache License, Version 2.0.
Software developers can find much more information about the OpenMx project at the OpenMx Developer Forums or looking at the About OpenMx page.