See below for an earlier version of Franklin that should work on older Macs. It was last compiled in 2012 as a 64 bit application.
Franklin X is a Macintosh application for plotting electric field lines and equipotential surfaces around point charges. It has been updated from earlier versions written some years ago. It is now programmed in Swift and uses Metal instead of OpenGL for 3D graphics. Franklin X is intended as freeware for science education.
In making this webpage, the online html tutorial at tutorialrepublic.com proved invaluable.