Netscape calendar 4.71 is expecting /lib/ld-linux.so.1 which doesn't exist in RedHat 7.0. Would it be a good idea to include a ld.so-1.x.x compatibility package? I believe RedHat 6.2 had both the glibc-2.1.3 ld.so as well as the 1.x.x ld.so.
We cannot support prehistoric binaries indefinitely, ld.so and libc5 packages were dropper on purpose from the distribution. If you need libc5 compatibility, you can always install ld.so and libc5 packages from RH 6.2.