Remembering from last time that now there's no g77, we're using g95 instead:
$ g95 -v -G -flat_namespace -fPIC -c looptempslin1.f

$ gcc -v -fPIC -c -flat_namespace wraplooptempslin1.c

$ gcc -bundle  -flat_namespace -dynamic -lm -lc -undefined suppress -o looptempslin1.so wraplooptempslin1.o looptempslin1.o
IDL> @flareworkshop_101706a
% CALL_EXTERNAL: Error loading sharable executable.
Symbol: wraplooptempslin1, File = looptempslin1.so
dlopen(looptempslin1.so, 1): Library not loaded:
/usr/local/lib/libgcc_s.1.0.dylib
Referenced from: looptempslin1.so
Reason: image not found
% Execution halted at: SYNSOLAR_CALLEXTERNAL 451

Look for /usr/local/lib/libgcc_s.1.0.dylib
Searched using spotlight for libgcc_s.1.0.dylib: found it in two locations, picked one
(the other was /Developer/SDKs/MacOSX10.3.9.sdk/usr/lib/)

Take the direct, kludgy approach and just symlink it into the directory where gcc (g95? idl??) appears to be looking for it:

/usr/local/lib $ sudo ln -s /usr/local/g95-install/lib/gcc-lib/i386-apple-darwin8.7.1/4.0.3/libgcc_s.1.0.dylib .
Password:
/usr/local/lib $ 
/usr/local/lib $ ls -l libgcc_s.1.0.dylib
 lrwxr-xr-x 1root wheel 82 Oct 18 11:57 libgcc_s.1.0.dylib ->
/usr/local/g95-install/lib/gcc-lib/i386-apple-darwin8.7.1/4.0.3/libgcc_s.1.0.dylib

I think I recompiled everything and restarted IDL in between this and the next step.

Now the problem is different:

% CALL_EXTERNAL: Error loading sharable executable.
                 Symbol: wrapchsq2bb, File = chisq2bb.so
                 dlopen(chisq2bb.so, 1): image not found
% Execution halted at: CHISQFITSPECTRA9B  431

[Re-] Compile yet another fortran program:

~/Documents/Astro/Program06Tiryns $ g95 -flat_namespace -c chisqinloop2bb.f 
tiryns:~/Documents/Astro/Program06Tiryns $ gcc -flat_namespace -c wrapchisq2bb.c
i686-apple-darwin8-gcc-4.0.1: wrapchisq2bb.c: No such file or directory
i686-apple-darwin8-gcc-4.0.1: no input files
~/Documents/Astro/Program06Tiryns $ gcc -flat_namespace -c wrapchsq2bb.c
wrapchsq2bb.c: In function 'wrapchsq2bb':
wrapchsq2bb.c:32: warning: assignment from incompatible pointer type
wrapchsq2bb.c:33: warning: assignment from incompatible pointer type
wrapchsq2bb.c:34: warning: assignment from incompatible pointer type
~/Documents/Astro/Program06Tiryns $ gcc -bundle -flat_namespace -o chisq2bb.so wrapchsq2bb.o chisqinloop2bb.o
~/Documents/Astro/Program06Tiryns $ 

Version: /home/lucy/Astro/XRS/Program/LL/day2date.pro
% Compiled module: JULDATE.
% Compiled module: MAKEGOESRESULTS.
HCOVERLAMBDA    DOUBLE    = Array[3934]
% Attempt to call undefined procedure/function: 'GOES_TF'.
% Execution halted at: MAKEGOESRESULTS    99
  /Users/Lucy/Documents/Astro/Program06Tiryns/makegoesresults.pro
%                      FITFLARE_101706A  401
  /Users/Lucy/Documents/Astro/Program06Tiryns/fitflare_101706a.pro
%                      ANFLARE_HOME       68
  /Users/Lucy/Documents/Astro/Program06Tiryns/anflare_home.pro
%                      $MAIN$          

After copying goes_tf.pro into the working directory and changing a few other variables (notably "goesdir" in fitflare_101706a.pro) for the working system, now it works! Yay!

(I also copied the entire /ssw directory into ~/Idl, so that it would be in the !PATH, but for whatever reason that doesn't seem to have worked!)