Die K Desktopumgebung

4.16 Installing Redhat packages says "libncurses.so.3.0 is needed"

If there isn't a rpm for it on your Redhat CD, poke around the Redhat FTP site and its mirrors to get it. Do bear in mind that libncurses-3 and -4 coexist so there is no need to replace one with the other, i.e. a plain rpm -i will do.

Or you might try the following:
 cd /usr/lib
 ln -s libncurses.so.4 libncurses.so.3
 ldconfig
 rpm -i --nodeps kdebase...

Since libncurses-3 and -4 are 100% compatible both at binary and at source level, installing two versions is just a waste of space.