There is no ktalkd in KDE4 (which ships with Slackware 13.0), you will need KDE3 for that.
The inetd package is KDE-agnostic. It only provides a configuration file which allows you to start services if the corresponding binaries are available on your computer. There is no reason why the inetd.conf file should have to be updated when one of the services goes missing. Who can tell if you might install that service from another source?
If you want ktalkd, you will have to remove KDE4 and instead, install
KDE 3.5.10 for Slackware 13.0.
Eric