This will be a command line program, reading a dxf file and saving a converted dxf file, with splines converted to biarcs.
There were errors reading splines with OpenCASCADE 6.9, so I'm going to try 7.3
To build on Windows ( I haven't finished trying this... )
Download Microsoft Visual Studio 2017 Community Edition ( OpenCASCADE 7.3 has pre-built binaries for Visual Studio 2010 and 2017 ).
Download OpenCASCADE 7.3 with pre-built binaries for VS 2017.