This chapter provides an overview over the current spectrum of free and open source licensed geospatial software tools and communities.

The number of available open source geospatial tools continues to grow and diversify, while new fields of application emerge. This chapter presents a selection of well-established free and open source software (FOSS) tools as reference cases, including software libraries, desktop applications, web mapping, databases, and use with portable devices, mostly based on the portfolio of FOSS tools, which is curated and maintained by the metaproject OSGeoLive, which is also discussed in this chapter.

FOSS software options are available for almost any kind and magnitude of geospatial task, for some niche tasks, they can even be the only options. Geospatial FOSS are available for portable devices, desktop machines, high-performance cluster environments, as Web-based applications or Software-as-a-Services (SaaS) in cloud environments. While a range of different open source licenses exists and are applied to geospatial software, they all adhere to the same key principles of openness and freedom for the user, most notably the rights to run the program, access the source code for study and improvements, and to redistribute copies of the program and its modifications.

This allows for transparency of the computations, as the source code implementation of all algorithms can be verified and possibly improved when necessary. Also public access to the code base ensures sustainable long term availability of the software tool to the users.

FOSS geospatial software has proven to be just as reliable and suitable for professional use as closed-source software alternatives. As a service to the readers, the reference section of this chapter includes scientific video recordings which provide additional content regarding software capabilities, historical notes and background information: Actinia 1 , GeoBlackLight 2 , GeoPaparazzi 3 ; 4 , GeoPython 5 ; 6 ; 7 , GeoServer 8 ; 9 , GeoTools 9 , GMT 10 , GRASS GIS 11 ; 12 ; 13 ; 1 , gvSIG 14 ; 15 ; 3 ; 16 , JTS 17 , Leaflet 18 , MapServer 19 ; 20 , NASA World Wind 16 , OSGeoLive 21 , PostGIS 22 , PROJ 23 ; 24 , QGIS 25 , rasdaman 26 . In addition, scientific videos about the OSGeo Foundation 27 and the annual Sol Katz Awards or Geospatial Free and Open Source Software 28 ; 29 are included.