This source code of HYDRUS-1D is modified from the original "(open) source code of the direct computational module of HYDRUS-1D" downloaded from here. It is released under GPL-3 and their original source code is available in the pc-progress branch. The original source code was converted from DOS to UNIX format using dos2unix.
The original code fails to compile with GNU Fortran, but the master branch includes modifications that allow it to compile successfully.