The geospatial extension (PostGIS) built into Postgres Plus is an open source geogpahic information server. PostGIS spatially enables the Postgres Plus server, allowing it to be used as a backend spatial database for geographic information systems (GIS), much like ESRI's SDE or the Oracle Database Spatial Extension. PostGIS follows the OpenGIS "Simple Features Specification for SQL" and has been certified as compliant with the "Types and Functions" profile.
Read the Case Study on FortiusOne's use of Postgres Plus with geospatial extensions or see it in action at www.fortiusone.com