First of all: Eclipse has better support for Maven projects on each version. So, to avoid headaches, just download the latest eclipse available.Eclipse has many installer tutorials, so I won’t stop here explaining how to run eclipse. I will just assume you know how to do it.
To run GeoNetwork from eclipse is very very easy. Just right click on the Package Explorer view to import -> As Maven Project over the folder you already had cloned on the last post:
The source code is available on a public repository on Github. This means that you can clone, fork and propose pushes of your custom changes. If you are not familiar with repositories of code or git, you should check this quick manual.
GeoNetwork is a server side application that allows you to maintain a geographic referenced metadata catalogue. This means: a search portal that allows to view metadata combined with maps.
Based on Free and Open Source Software, it strictly follows different standards for metadata, from Inspire to OGC. It implements the CSW interface to be able to interact with generic clients looking for data. It also has built-in harvesters to connect to other servers and populate data.
The catalogue deploys on a java application container (like tomcat or jetty). It works over the Jeeves framework. Jeeves is based on XSLT transformation server library. This allows a powerful development of interfaces, for humans (HTML) or machines (XML). Therefore, it makes metadata from GeoNetwork to be easily accessible by different platforms.
Recently half-refactored to Spring and AngularJS, GeoNetwork has a REST API and an event hook system to make extensions and customizations easier.