There are occasions where plugins require jar files added to jEdit's classpath. The normal jEdit JarClassloader does not suffice in these circumstances as these jars need to be a part of the System classloader.
To fix this jEdit should have a well known location where jar files can be added, and have them be part of jEdit's system classloader. This can be a /lib, or /shared directory under the jEdit installation directory, or under the jEdit settings directory.
It would be nice if there was an interface within jEdit to install jars into this directory - a restart of jEdit would be OK in my opinion. There should be some way of doing this programmatically as well - perhaps jEdit.getSharedLibDirectory(). A plugin should be able to take jars from it's package and install them into this directory and ask the user to restart jEdit.