MapServer is a graduated OSGeo project.
From the OSGeo homepage:
MapServer is an open source development environment for building spatially-enabled web mapping applications and services. It is fast, flexible, reliable and can be integratated into just about any GIS environment. Originally developed at the University of Minnesota, MapServer is now maintained by developers around the world.
MapServer runs on all major operating systems and will work with almost any web server. MapServer features MapScript, a powerful scripting environment that supports many popular languages including PHP, Python, Perl, C# and Java. Using MapScript makes it fast and easy to build complex geospatial web applications.
MapServer is supported by a vibrant user community so help is just an email away. Because MapServer is open source you get the source code so it is possible to extend the software to exactly meet your needs.
- Supports industry standard data formats and spatial databases
- On-the-fly feature classification
- Sophisticated rule-based labeling
- On-the-fly projection for both raster and vector data
- Provides a wide variety of spatial and attribute-based queries
- Supports popular Open Geospatial Consortium (OGC) standards including WMS, WFS and WCS
- Leverages best-of-breed open source geospatial technologies such as GDAL/OGR, PostGIS and PROJ.4
- Integrates with popular front-end environments such as OpenLayers, ka-Map, Chameleon, Mapbender, MapFish, Cartoweb, and many, many others.