GRASS - Geographic Resources Analysis Support System is a general GIS supporting processing, analysis and display of raster, vector, site and imagery data, geospatial simulations and visualization.

Overview of GRASS versions currently available:
 

• CVS GRASS - continuously updated developers version
• GRASS5.1     - under development
• GRASS5.0      - latest stable release XX.XX.2001
• floating point and NULL added (note removal of LZW starting GRASS5.0beta11)
• multidimensional/multiattribute site format
• tcltkgrass
• GRASS4.2     - ...
• GRASS4.1     - latest official CERL release 1991

GRASS is an Open source sofware released under the GNU General Public Licence - it is therefore free with protection of the authors' rights. With its 1.5 million lines of C code it belongs to the Top10 Open source projects.