GeoServer is an open source software server written in Java that allows users to share and edit geospatial data. Designed for interoperability, it publishes data from any major spatial data source using open standards.
GeoServer is the reference implementation of the Open Geospatial Consortium (OGC) Web Feature Service (WFS) and Web Coverage Service (WCS) standards, as well as a high performance certified compliant Web Map Service (WMS). GeoServer forms a core component of the Geospatial Web.
The Enterprise version of the GeoServer has been developed by GeoSolutions reusing the community version of GeoServer itself. It contains some standard extension plus some additional one developed by GeoSolutions. It is released as Open Source under the GPL v 2.0 license.
The code lives in the supported branches (e.g., 2.2.x at the moment)