Here is the fortran 77 compiler for Mac OS X.
http://hpc.sourceforge.net/
We downloaded the g77 (second item on the page)

installation command is: sudo tar xvf g77...tar -C /

To get the file to run, it must be marked executable.
From terminal, run the following command in the directory where the
file has been downloaded:
 
 chmod ug+x bzams1




Here is the bug I got. Deleting line 4 from the code eliminates the  
first error, and then the remaining should be non-fatal.

bzams1.for:4:
    $DEBUG
    ^
Invalid first character at (^) [info -f g77 M LEX]
bzams1.for: In subroutine `odeint':
bzams1.for:26: warning:
          common /path/ kmax,kount,dxsav,xp(KMAXX),yp(NMAX,KMAXX)
                  1
bzams1.for:4187: (continued):
          COMMON /PATH/ KMAX,KOUNT,DXSAV,XP,YP
                  2
Common block `path' is 816016 bytes in length at (1) but 8160016  
bytes at (2)


______________________
Andy Green
Senior in Astrophysics
California Institute of Technology