Question: How many different kinds of softwares have been released under the GPL license?
SPARQL query:
PREFIX prop: <http://dbpedia.org/property/>
PREFIX onto: <http://dbpedia.org/ontology/>
SELECT DISTINCT COUNT(?uri) WHERE { ?x prop:license <http://dbpedia.org/resource/GNU_General_Public_License> . ?x onto:genre ?uri  . }