on 
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=297582
the bug reporter said something about patching:
-------------
With the attached patch 'gnuchess' can be compiled
on amd64 using gcc-4.0.
Regards
Andreas Jochens
diff -urN ../tmp-orig/gnuchess-5.07/src/common.h ./src/common.h
--- ../tmp-orig/gnuchess-5.07/src/common.h    2003-06-30 13:28:38.000000000 +0200
+++ ./src/common.h    2005-03-01 18:01:50.629624486 +0100
@@ -716,7 +716,6 @@ 
 /* Input thread and thread function */
 #include <pthread.h>
-extern pthread_t input_thread;
 void *input_func(void *); 
 /*
------------
which line(s) and how?