In 1985, EGS was interfaced to the old FLUKA (the version which
became known as FLUKA86), four years before the modern FLUKA was born.
For several years, starting in 1989, many changes were made to the
treatment of electrons and photons in the new code, eliminating
approximations, modifying the existing physical models, adding new
effects and introducing new sampling techniques. 
The two codes EGS and EMF (ElectroMagnetic Fluka) where already de facto two
independent codes in 1992. Only some commonalities in a few parts of 
the cross section preprocessor were left: EMF had revised new physics 
for many processes.
The cross section preprocessor PEMF, although strongly modified, has
kept a memory of the EGS equivalent PEGS preprocessor until 2005.
In the meantime, the EGS program itself was modified by its authors
in completely different and independent directions.
The story of the development of the EMF part of FLUKA is narrated in
detail in the Manual (section 16.4.10 of the Yellow Report
CERN-2005-10).

The hadronic event generator of the FLUKA92 version was interfaced
with GEANT3 (version 3.15) around 1993, with the collaboration of
K. Lassila. That version of FLUKA, which was described in
A. Fasso`, A. Ferrari, J. Ranft and P.R. Sala, Proc. IV Int. Conf.
on Calorimetry in High Energy Physics, La Biodola (Italy) 21-26
September 1993, Ed. A. Menzione and A. Scribano, World Scientific,
p. 493-502
included the first implementation of the PEANUT preequilibrium
model (the so-called linear model). It has never been updated
and differs greatly from the present version. It should be 
considered obsolete and no longer used, but surprisingly it is still 
widely popular. To avoid confusion with today's FLUKA, that version must be
referred to as G-FLUKA. Some extra informations can be found in the
ATLAS Internal Note PHYS-NO-086, (28 pages) (1996) which can be
easily found from the CERN Web site.
   
A special package, FLUGG, has been written to allow the use of FLUKA
with the GEANT4 geometry. Instructions and detailed examples are
available on the FLUKA web page:
http://www.fluka.org/projects/flugg/

A very old version of the FLUKA hadron generator, the so-called 
EVENTQ contained in FLUKA87 with some corrections made around 1989,
was included in the LAHET program and was later inherited by
MCNPX. That version has very little in common with the modern
FLUKA.
Some other exchanges took place between FLUKA and LAHET (but not
MCNPX). In 1993 the RAL high-energy fission model by Atchison was
kindly provided by R.E. Prael as implemented in LAHET. Since then
the model has undergone important modifications and improvements
and little is now left of the original implementation. On the
other hand, the event generator which was in FLUKA till spring 1997
was made available to R. Prael in 1997 but it is not included
in MCNPX.

The hadron event generator of FLUKA has been interfaced to CORSIKA
in 2003. Only the part between 50 MeV and 80 GeV has been included.
The version in CORSIKA is constantly being kept up to date with the
current FLUKA version.