Wikidata offers copies of the available content for anyone to download.
Note that there are also several other methods for accessing structured content from Wikidata, which may not require a complete database dump.
JSON dumps (recommended)
JSON dumps containing all Wikidata entities as a list can be found at http://dumps.wikimedia.org/other/wikidata/. Those are being created on a weekly basis.
This is the recommended dump format. Please refer to the JSON structure documentation for information about how Wikidata entities are represented.
Hint: Each entity object (data item or property) is placed on a separate line in the JSON file, so the file can be read line by line, and each line can be decoded as a JSON object. Note that the entries in the dump do not have to be in order: Q2 doesn't necessarily follow Q1.
Full XML dumps of Wikidata can be found at http://dumps.wikimedia.org/wikidatawiki/.
Incremental dumps (or Add/Change dumps) for Wikidata are also available for download. These dumps contain stuff that was added in the last 24 hours, reducing the need of having to download the full database dump. These dumps are considerably smaller than the full database dumps
They can be found at http://dumps.wikimedia.org/other/incr/wikidatawiki/.
Complete, simplified and derived dumps can be found at http://tools.wmflabs.org/wikidata-exports/rdf/. The RDF encoding that is used is described in the paper Introducing Wikidata to the Linked Data Web.
The complete dumps together contain all entity information in Wikidata with the exception of order (of aliases, of statements, etc.), which is not naturally represented in RDF. Simplified dumps encode statements that have no qualifiers as single RDF triples (references are omitted).
The data model can be looked up here. The data model describes the fundamental building blocks of Wikidata's data.
An overview over the schema of the database can be found at this page. (This is not the schema of the data in Wikidata.)
These databases can be used for personal or commercial use, backups or offline use. All structured data from the main and property namespace is available under the Creative Commons CC0 License. Text in the other namespaces is available under the Creative Commons Attribution/Share-Alike License; additional terms may apply. Media items and other content are available under other licenses, as detailed on their description pages.