Only the Geant3.21 code itself and the implementation of the TVirtualMC interface, TGeant3, provided in geant3 are maintained by the VMC project.
The updated version of Geant3.21 that includes several bug fixes compared to the standard version in CERNLIB. In this version all Geant3 gxxxxx routines have been renamed g3xxxxx.
The old Makefile system was replaced with a CMake based system since version 2.0.
See also Geant3.21 User Guide
The directory TGeant3 contains the classes TGeant3 and TGeant3TGeo,
which implement the TVirtualMC interface, see more about VMC at:
https://root.cern.ch/vmc
The directory examples includes a set of FORTRAN examples. These examples are not maintained and tested in the VMC project test suites. Instead, the geant3 package is tested using the test suites defined in geant4_vmc/examples.