This did the trick
Omitting the addClasspath and adding manifestEntries
Now, log4j.properties can reside outside the jar - and still be found...
<manifest>
<addClasspath>true</addClasspath>
</manifest>
This is working:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<configuration>
<archive>
<manifestEntries>
<Built-By>Me</Built-By>
<Class-Path>.</Class-Path>
</manifestEntries>
</archive>
</configuration>
</plugin>
Output:
Manifest-Version: 1.0
Archiver-Version: Plexus Archiver
Created-By: Apache Maven
Build-Jdk: 1.6.0_45
Built-By: Me
Class-Path: .