Free database management systems

HBase is an open source, non-relational, distributed database modeled after Google's BigTable and is written in Java.

MariaDB is a community-developed fork of the MySQL relational database management system intended to remain free under the GNU GPL.

MyISAM was the default storage engine for the MySQL relational database management system versions prior to 5.

Redis is a software project that implements data structure servers.

Riak is a distributed NoSQL key-value data store that offers high availability, fault tolerance, operational simplicity, and scalability.

RRDtool (round-robin database tool) aims to handle time series data such as network bandwidth, temperatures or CPU load.

Couchbase Server, originally known as Membase, is an open-source, distributed (shared-nothing architecture) multi-model NoSQL document-oriented database software package that is optimized for interactive applications.

H2 is a relational database management system written in Java.

Neo4j is a graph database management system developed by Neo Technology, Inc.

Metakit is an embedded database library with a small footprint.

PostgreSQL, often simply Postgres, is an object-relational database (ORDBMS) – i.

RethinkDB is an open source, NoSQL, distributed document-oriented database.

MongoDB (from humongous) is a free and open-source cross-platform document-oriented database program.

The Zope Object Database (ZODB) is an object-oriented database for transparently and persistently storing Python objects.

Kexi is a visual database applications creator tool by KDE, designed to fill the gap between spreadsheets and database solutions requiring more sophisticated development.

OrientDB is an open source NoSQL database management system written in Java.

db4o (database for objects) was an embeddable open source object database for Java and .

VoltDB is an in-memory database designed by Michael Stonebraker (who was involved in Ingres and POSTGRES), Sam Madden, and Daniel Abadi.

Sedna is an open source database management system that provides native storage for XML data.

Percona XtraDB is a storage engine for the MariaDB and Percona Server databases, and is intended as a drop-in replacement to InnoDB, which is one of the default engines available on the MySQL database.

Berkeley DB (BDB) is a software library intended to provide a high-performance embedded database for key/value data.

InnoDB is a storage engine for MySQL.

Apache CouchDB is open source database software that focuses on ease of use and having an architecture that "completely embraces the Web".

eXist is an open source software project for NoSQL databases built on XML technology.

Mnesia is a distributed, soft real-time database management system written in the Erlang programming language.

HSQLDB (Hyper SQL Database) is a relational database management system written in Java.

BaseX is a native and light-weight XML database management system and XQuery processor, developed as a community project on GitHub.

Ingres Database (/ɪŋˈɡrɛs/ ing-GRESS) is a commercially supported, open-source SQL relational database management system intended to support large commercial and government applications.

Apache Cassandra is a free and open-source distributed database management system designed to handle large amounts of data across many commodityservers, providing high availability with no single point of failure.

Apache Derby (previously distributed as IBM Cloudscape) is a relational database management system (RDBMS) developed by the Apache Software Foundation that can be embedded in Java programs and used for online transaction processing.

CUBRID (/ˈkjuːbrɪd/ "cube-rid") is an open source SQL-based relational database management system (RDBMS) with object extensions developed by Naver Corporation for web applications.

Rasdaman ("raster data manager") is an Array DBMS, that is: a Database Management System which adds capabilities for storage and retrieval of massive multi-dimensional arrays, such as sensor, image, and statistics data.

Rel is an open source true relational database management system that implements a significant portion of Chris Date and Hugh Darwen's Tutorial D query language.

Tarantool is an open-source NoSQL database management system and Lua application server.

txtSQL (pronounced "text-sequel") is an object-oriented (OOP) flat-file database management system written in PHP.

Virtuoso Universal Server is a middleware and database engine hybrid that combines the functionality of a traditional RDBMS, ORDBMS, virtual database, RDF, XML, free-text, web application server and file server functionality in a single system.

Neo (or .NET Entity Objects) is an object-relational mapping (ORM) solution for the Microsoft .

Druid is a column-oriented, open-source, distributed data store written in Java.

TokuMX is an open source distribution of MongoDB which, among other things, replaces the default B-tree data structure found in the basic MongoDB distribution with a Fractal tree index.

WebScaleSQL is an open-source relational database management system (RDBMS) created as a software branch of the production-ready community releases of MySQL.

TokuDB is an open source, high-performance storage engine for MySQL and MariaDB.

Raindrop is a messaging application building on Apache's CouchDB which is used through a web interface.

GNOME-DB is a database application by the GNOME community.

Wakanda (a.k.a "Wakanda App Factory") is a W-RAD (Web Rapid Application Development) as well as M-RAD (Mobile Rapid Application Development), designed for creating multi-channel applications for mobile, web and desktop.

Trafodion is a database management system that runs on top of Hadoop, providing support for transactional or operational workloads in a big data environment.

HyperDex is an open source distributed data store.

Drizzle is a free software/open source relational database management system (DBMS) that was forked from the now-defunct 6.

Infobright is a commercial provider of column-oriented relational database software with a focus in machine-generated data.

Aerospike is a flash-optimized in-memory open source NoSQL database and the name of the company that produces it.

Perst is an open source, dual license, object-oriented embedded database management system (ODBMS).

MemcacheDB (pronunciation: mem-cash-dee-bee) is a persistence enabled variant of memcached, a general-purpose distributed memory caching system often used to speed up dynamic database-driven websites by caching data and objects in memory.

Percona Server is a fork of the MySQL relational database management system created by Percona.

Strozzi NoSQL is a shell-based relational database management system initialized and developed by Carlo Strozzi that runs under Unix-like operating systems, or others with compatibility layers (e.g., Cygwin under Windows).

FlockDB is an open source distributed, fault-tolerant graph database for managing wide but shallow network graphs.

Gadfly is a relational database management system written in Python.

Gizzard is an open source sharding framework to create custom fault-tolerant, distributed databases.

H-Store is an experimental database management system (DBMS) designed for online transaction processing applications that is being developed by a team at Brown University, Carnegie Mellon University, the Massachusetts Institute of Technology, and Yale University.

EnterpriseDB (EDB) is a privately held company that provides software and services based on the open source database PostgreSQL.

Apache Accumulo is a computer software project that developed a sorted, distributed key/value store based on the BigTable technology from Google.

Sones GraphDB was a graph database developed by the German company sones GmbH, available from 2010 to 2012.

NoSQLz is a consistent key-value Big data store (NoSQL database) for z/OS IBM systems.

Hibari is a strongly consistent, highly available, distributed, key-value Big Data store.

MonetDB is an open source column-oriented database management system developed at the Centrum Wiskunde & Informatica (CWI) in the Netherlands.

MySQL (officially pronounced as /maɪ ˌɛskjuːˈɛl/ "My S-Q-L",) is an open-source relational database management system (RDBMS).

GT.M is a high-throughput key-value database engine optimized for transaction processing.

GCstar is an open source application for managing personal collections.

There are ORMs to manage a database: * django (web framework) * SQLObject * others

LucidDB is an open source database purpose-built to power data warehouses, OLAP servers and business intelligence systems.

Dataphor is an open-source truly-relational database management system (RDBMS) and its accompanying user interface technologies, which together are designed to provide highly declarative software application development.

TreapDB is a kind of NoSQL data store, and it is based on Treap data structure.

CSQL is an open source main memory high-performance relational database management system developed at sourceforge.

InfiniDB (formerly Calpont Corporation) was a database management software company based in Frisco, Texas.

Couchbase, Inc. is a private software company that develops and provides commercial packages and support for Couchbase Server and Couchbase Lite both of which are open-source, NoSQL, multi-model, document-oriented database that store JSON documents or a pure key-value database.

Database Deployment Manager (DDM) is an open source desktop oriented multi-platform database design tool that allows database administrators and/or programmers to create database structures (using an object oriented methodology) and deploy them into an existing database.

Database Management Library (DBL) is a relational database management system (RDBMS) contained in a C++ programming library.

Hypertable was an open-source software project to implement a database management system inspired by publications on the design of Google's BigTable.

SciDB is an array database designed for multidimensional data management and analytics common to scientific, geospatial, financial, and industrial applications.