diff -ur ugs.orig/Imakefile.def ugs/Imakefile.def
--- ugs.orig/Imakefile.def	2007-12-07 20:45:08.000000000 +0900
+++ ugs/Imakefile.def	2008-09-02 08:27:40.000000000 +0900
@@ -8,6 +8,7 @@
 /* #define DigitalArchitecture */
 /* #define FreeBSDArchitecture */
 /* #define AIXArchitecture */
+/* #define DarwinArchitecture */
 
 /*-------------- Do not change the followings ---------------*/
 
@@ -76,6 +77,17 @@
 LDOPT   = -brename:.malloc_,.malloc -brename:.free_,.free
 #endif
 
+#if defined(DarwinArchitecture)
+ARCH    = __Darwin
+FC      = g95
+FFLAGS  = -O2 -fstatic -fzero -fno-backslash
+CC      = cc
+CFLAGS  = -O2
+AR      = ar
+ARFLAGS = rsv
+RANCMD  =
+#endif
+
 /*--------------------- General Rules ------------------------*/
 
 .f.o:;\
diff -ur ugs.orig/src.2.10e/Imakefile ugs/src.2.10e/Imakefile
--- ugs.orig/src.2.10e/Imakefile	2006-05-19 17:06:53.000000000 +0900
+++ ugs/src.2.10e/Imakefile	2008-09-02 08:22:25.000000000 +0900
@@ -133,3 +133,8 @@
         $(AR) $(ARFLAGS) $(LIB)  $*.o
 #endif
 
+#if defined(DarwinArchitecture)
+ugdupl.o:;\
+	fort77 -c -O2 -Nq300 -\!bs $*.f  ;\
+	$(AR) $(ARFLAGS) $(LIB)  $*.o
+#endif
diff -ur ugs.orig/src.2.10e/aux.c ugs/src.2.10e/aux.c
--- ugs.orig/src.2.10e/aux.c	1996-05-19 17:27:04.000000000 +0900
+++ ugs/src.2.10e/aux.c	2008-09-02 07:54:04.000000000 +0900
@@ -1,6 +1,6 @@
 #include <stdlib.h>
 
-#if ( defined(__LINUX_AOUT) || defined(__LINUX_ELF) )
+#if ( defined(__LINUX_AOUT) || defined(__LINUX_ELF) || defined(__Darwin) )
 void free_   ( idum )   void *idum ;  { free (idum) ; }
 void malloc_ ( idum ) size_t *idum ;  { malloc (*idum) ; }
 #endif
diff -ur ugs.orig/src.2.10e/uge002.F ugs/src.2.10e/uge002.F
--- ugs.orig/src.2.10e/uge002.F	1996-05-19 17:24:00.000000000 +0900
+++ ugs/src.2.10e/uge002.F	2008-09-02 07:40:19.000000000 +0900
@@ -192,7 +192,8 @@
   301   IF (DATA(PTCT+INT2).NE.CHAR) THEN
   302     IF (INT2.GT.(INT1+1)) THEN
             INT3=(INT1+INT2)/2
-#if  ( defined(__LINUX_AOUT) || defined(__LINUX_ELF) || defined(__OSF1) )
+#if  ( defined(__LINUX_AOUT) || defined(__LINUX_ELF) || defined(__OSF1) ||\
+       defined(__Darwin) )
 c      This is a little-endian architecture
        IF (DATA(PTCT+INT3).GE.CHAR) THEN
 #else
diff -ur ugs.orig/src.2.10e/ugz005.F ugs/src.2.10e/ugz005.F
--- ugs.orig/src.2.10e/ugz005.F	2007-12-07 22:16:11.000000000 +0900
+++ ugs/src.2.10e/ugz005.F	2008-09-02 07:52:47.000000000 +0900
@@ -23,7 +23,7 @@
 *                                                                   *
 *********************************************************************
 
-#if   defined(__AIX)
+#if ( defined(__AIX) || defined (__Darwin) )
       DADR =  LOC(DATA)
 #else
       DADR = %LOC(DATA)