GribApi.Native is an interop shim for GribApi.NET. It licensed under the friendly Apache License 2.0.
Most of the interop interfaces are generated using SWIG and included in the repository. You shouldn't need to create them. However, if you want to generate the interfaces yourself, you'll need SWIG installed and available on PATH. Then run build/win32/swig_gen.cmd. The .cs files are written to build/SWIG
You can build from Visual Studio or using the build script:
> build/win32/build_gribapi.cmd [rebuild|build] [tools version]
E.g., for VS 2015
> build/win32/build_gribapi.cmd rebuild 14