Obtained from https://upjv.q4md-forcefieldtools.org/RED/ together with
other programs in q4md-fft tools 2.0. I was not aware of this version,
since the hosted documentation talks about version 2.2 and the download
process must've been different, because I was able to download
"standalone resp", which was also version 2.2.
Not sure why the html documentation and license statement are missing.
The comment at the top of `resp.f` lists no version 2.3 and the embedded changelog states:
C RESP standalone version 2.4:
C
C Change mol for mep (Molecular Electrostatic Potentail).
C Same input for single-MEP and multi-MEP fits
C (balnk line required before Intra-Molecular-Charge-Constraint).
C Can handle larger MEP grid (up to 999,999 points).
C Parameters in shared_variables.h.
C Restraint from Henchman and Essex to compute OPLS charges.
C Correction of the traceless quadrupole moments.
C Computation of traceless quadrupole moments for
C multi-Molecular-Electrostatic Potantial.
C Modification of esout file.
C Introduction of esqpotpdb, asmpotpdb and, espdb files
C to assess the quality of the fit.
C Computation of r2.
C Correction of the standard error of estimate
C
C Authors: J.-P. Becker, F. Wang, P. Cieplak & F.-Y. Dupradeau
C http://q4md-forcefieldtools.org/