There are a few problems with some of the packages supplied by some of the Linux vendors.
The X Font Server package (XFS) that ships with Redhat 6.0 does not handle serving fonts to remote workstations. Newer versions of xfs are fine, and you can upgrade the xfs on Redhat 6.0 and it will work properly. See the installation instructions on 'Setting up the server' for information on how to upgrade xfs. If you don't use XFS, then you don't need to upgrade it.
The /usr/sbin/inetd program supplied with RedHat 6.2 has a problem after it has spawned about 40 invokations of tftpd. It will just refuse to spawn any additional tftpd processes until the server is rebooted. There isn't any mention on Redhat's errata page, but the problem goes away if you use a version of init from an older version of Redhat.
Caldera doesn't include the tftp daemon on the eDesktop version of their Linux distribution. You can get the tftp RPM from the eServer CD. The RPM from eServer v2.3 is called netkit-tftp-0.10-2.i386.rpm.