We also provide a distribution of the OpenSim source code via a zip file (starting with 3.0) and access to the OpenSim project repository on GitHub. This allows you to see the details of the algorithms underlying OpenSim and, if you build the source code, you can more easily debug the code you use to extend OpenSim. Please note that building from the source is challenging and, as a non-commercial entity, we have limited resources to provide support for the build process. This is an additional reason we encourage the use of the API and plug-ins.
In reviewing the OpenSim source code, if you discover what you think is an error in the code or an unexpected result, let us know by contacting the project team at firstname.lastname@example.org or filing an issue report on GitHub or a bug report on Simtk.org.
At the next level, advanced developers can create a pull request on GitHub to add a new feature, fix a bug, or make other improvements to the code. If you have a well-documented and well-tested plug-in or other utility, we would love to make it part of the main OpenSim distribution so that all users have easy access to it. More details about how to make a contribution to the OpenSim code, via pull request on GitHub, are described below.
The above details apply to the OpenSim API. The OpenSim GUI will be moving to GitHub in the coming months, as well. We'll provide more details about GUI contributions then.
OpenSim Source Contribution Policy
See the Guidelines for Contributing on GitHub.