as suggested, added a comment, why NetBSD needs a higher memory limit
MODIFY
include/config.h
include/config.h
# else
# define MEM_LIMIT 50
# endif /* ^!WORD_SIZE_64 */
-#else
+#else /* NetBSD's kernel needs more space for stack, see discussion for issue #165 */
# define MEM_LIMIT 200
#endif
/* Default memory limit when running in QEMU mode (MB): */

as suggested, added a comment, why NetBSD needs a higher memory limit