OpenSCAD User Manual/CSG Export
The CSG Format is a subset of the OpenSCAD file format.
Being a subset, CSG is much easier to read/interpret for other CAD software, then a direct OpenSCAD File.
Currently, FreeCAD can import CSG, but it does not support the full format.
Using FreeCAD, OpenSCAD files can be converted into step files. (Of course, the limitations of the FreeCAD import have to be kept in mind, when using FreeCAD as a converter.)