Hi,
I have started the process of deploying Geonetwork artifacts to Maven Central so that anyone can easily build off of Geonetwork without having to build the project.
The ticket I have opened is:
https://issues.sonatype.org/browse/OSSRH-4462
If you are interested in the details of how to work with Maven central there are some instructions at:
https://docs.sonatype.org/display/Repository/Sonatype+OSS+Maven+Repository+Usage+Guide
Jesse