Before we start on the cooperation of Geomajas and GeoServer, there is the issue of where to store your data. If you intend to store it in a database, then you have many options. You can either have GeoServer render it without caching, and let it return WMS or WFS maps to Geomajas. But you could also configure your database directly into Geomajas, so you could eliminate the need to use GeoServer. Either way would work.