In the plugin install instructions for Solaris and Linux add the below.

Java Plug-in Product Installation Instructions

Add to 2. For Netscape 6 browsers: Use regxpcom tool provided by Netscape to
register Java Plug-in 1.4.

setenv LD_LIBRARY_PATH <Netscape 6>:$LD_LIBRARY_PATH

If you do not add Netscape to your LD_LIBRARY_PATH you will most likely get
an error when you run regxpcom. Something like, Open failed: No such file
or directory.


After running the regxpcom command you should get a message like below:
Registration successful for <jre>/plugin/i386/ns610/libjavaplugin_oji140.so


If regxpcom does not register the Java Plug-in successfully, (you get a
Registration failed message or a core dump) try creating a link to the Java
Plug-in libjavaplugin.so file in the Netscape 6 plugins directory.

cd <Netscape 6>/plugins
ln -s <JRE>/plugin/sparc/ns610/libjavaplugin_oji140.so .
Be sure to include the period at the end.


Note: Only one Java Plug-in can be registered at a time. When you want to use
a different version, unregister the one you have and register the new version.

regxpcom -u <absolute path to Java Plug-in libjavaplugin.so file>

Example:
regxpcom -u <JRE>/plugin/sparc/ns610/libjavaplugin_oji140.so

regxpcom <JRE>/plugin/sparc/ns610/libjavaplugin_oji141.so


Add to 3. For all Netscape browsers: Start your Netscape browser, or restart
it if it is already up.

In Netscape do Help -> About Plug-ins to see that the Java Plug-in is loaded.


The above was for Solaris. In the Linux install instructions change the above sparc to i386.