There are two Fortran 90 codes here.  The main code checks.f90 uses the module defs.f90 which contains some definitions.

The codes check that the tangential component of the electric field E and the normal component of the electric displacement D are continuous across the lipid-water interface at z' = 0 and across the lipid-cytosol interface at z' = -t.   Here z' = z - t/2 is the z-coordinate in the asymmetrical system of cordinates in which z' = 0 labels the lipid-water interface.