Faceposer

This tool is designed to edit choreography files in a special format designed for use with the Nuclide SDK. It can also edit choreographies in the VCD format used by Valves Source Engine.

It is written in C++ and uses the wxWidgets framework for its UI, which makes it cross platform (Windows, macOS, Linux).

You can see the projects source code in its git repository. Licensing is still pending, but it will most likely end up being released under a GPL variant.