Simply a fork of the legacy max-sdk for testing some jitter dev stuff. The example project to look at is in source/matrix/jit.matrixtests
Easiest is to clone the project into your Max Packages folder, that way the Max app will find the external with no extra configuration steps.
After cloning to Packages, navigate to the jit.matrixtests folder (or any other example), open the project file for your platform and click build. The project will build into the externals folder, and you can launch Max and instantiate a jit.matrixtests object.