<p>Freebase was "an open, Creative Commons Attribution (aka CC-BY) licensed collection of structured data," and a "platform for accessing and manipulating that data" via API. Almost 40 million entities and assertions about those entities are stored within a graph database. The database was built by pulling in open data and relies on community contribution to stay updated. Freebase was part of the semantic web and emits Linked Open Data (via RDF) for all its entities.</p>