Your /etc/profile file should have the following code in it:

export MOZILLA_HOME=/opt/netscape

export CLASSPATH=$MOZILLA_HOME/java/classes/ifc11.jar:
$MOZILLA_HOME/java/classes/jae40.jar:
$MOZILLA_HOME/java/classes/jio40.jar:
$MOZILLA_HOME/java/classes/ldap10.jar:
$MOZILLA_HOME/java/classes/iiop10.jar:
$MOZILLA_HOME/java/classes/java40.jar:
$MOZILLA_HOME/java/classes/jsd10.jar:
$MOZILLA_HOME/java/classes/scd10.jar
(note: take out the line breaks)

Note that the CLASSPATH indicates each of the files in the netscape/java/classes
directory. 

NOTE for 4.05: Should no longer need to set CLASSPATH, but I've found you do need
it in 4.5, better safe than sorry.

Because older versions of netscape have resided in /usr/local/netscape, I found
that it helps to create a symlink to /opt/netscape from there, like this:

ln -s /opt/netscape /usr/local/netscape

Note that current LinuxPPC installs like to do a ln -s /opt /usr/local by
default.

Performing a ln -s /opt/netscape /usr/local/netscape here would be, for
obvious reasons, a Grade A1 Bad Idea.

... and yet, I still can't get Netscape 4.5 to use Java properly in LinuxPPC R4.

I have my MOZILLA_PATH and CLASSPATH set appropriately, and have tried a fair
quantity of permutations (being exact about the /opt/netscape instead of using
$MOZILLA_PATH, using /usr/local/netscape instead of /opt/netscape, trying to use
the old Netscape 4.04 java files in /usr/lib/netscape/java/classes... etcetera).

Does Java work in the release version of Netscape 4.5 for anyone?

If so, what should I do to mine to make it work?