GRASS GIS (Geographic Resources Analysis Support System) is an open source, free software (FOSS) Geographical Information System (GIS) with raster, topological vector, image processing, and visualization functionality
MapWindow is an Open Source geographical information System that is free to Download. It is extensible, and as well uses and ActiveX control that allows custom programming. MapWindow Also supports the development of Plug-ins so that anyone...
GRASS GIS (Geographic Resources Analysis Support System) is an open source, free software (FOSS) Geographical Information System (GIS) with raster, topological vector, image processing, and visualization functionality