Apache CouchDB, commonly referred to as CouchDB, is a free and open source document-oriented database written in the Erlang programming language. It is designed for local replication and to scale vertically along a wide range of devices.

Overview

The founders of Postgres

Different people involved in PostgreSQL

PostgreSQL is an object-relational database management system (ORDBMS). It is released under a BSD-style license and is thus free software. As with many other open-source programs, PostgreSQL is not controlled by any single company, but relies on a global community of developers and companies to develop it.

MySQL is a relational database management system (RDBMS) which has more than 11 million installations. The program runs as a server providing multi-user access to a number of databases.
MySQL is owned and sponsored by a single for-profit firm, the Swedish company MySQL AB, now a subsidiary of Sun Microsystems,[3] which holds the copyright to most of the codebase. The project's source code is available under terms of the GNU General Public License, as well as under a variety of proprietary agreements.
"MySQL" is officially pronounced /maɪˌɛskjuːˈɛl/ (My S Q L), not "My sequel" /maɪˈsiːkwəl/. This adheres to the official ANSI pronunciation; SEQUEL was an earlier IBM database language, a predecessor to the SQL language. The company does not take issue with the pronunciation "My sequel" or other local variations.