Hi, FEATool Multiphysics is currently not fully open source, but the Matlab m-file source code for a subset of functionality is fully open, such as the
finite element definition library and
Matlab multiphysics script models, so that users can implement their own multiphysics models and finite element shape functions.
Moreover, with a full license you can still access and use the
FEATool m-file toolbox API in your own code (but not directly view, open, or modify those specific m-files). The relevant m-file stubs are installed with the toolbox (not via the github sources).