The bCNC is the application that connects to the Arduino GRBL. I do not know another application to do that, so I have to work with bCNC if I want to continue using the Arduino. I want to continue using the Arduino for various reasons even though this is not the best CNC platform.
Among the formats that can be opened by bCNC I can name the SVG and Gcode but not the Gerber.
I initially tried using the SVG generated by Fritzing but there is some incompatibility between the SVG exported by Fritzing and SVG imported by bCNC because no Fritzing SVG graphic can be imported into bCNC. This is a problem.
Another problem with the SVG graphic generated by Fritzing is that they can not be handled by Inkscape just as an SVG graphic generated by Inkscape can be handled by Inkscape itself. Try using the tools Union, Difference, Intersection, Exclusion, Division (in the Path tab) in SVGs generated by Inkscape and SVGs generated by Fritzing. If there was not a problem I could work the SVG graphic generated by Fritzing ( "xxx__etchcopper_bottom_mirror.svg") for the negativet it with the Exclusion tool.
So the solution would be to export a Gerber generated by Fritzing for Eagle generate Gcode to be used by bCNC but Gerber that Fritzing generates is not fully compatible with the Eagle and the result of the migration is unsatisfactory.
In my opinion the best solution would be obtained if the Fritzing generate SVG fully compatible with Inkscape's tools but this is not in my power.