SQLite

SQLite is an in-process library that implements a self-contained, serverless, zero-configuration, transactional SQL database engine. 

SQLite is the most widely deployed and used database engine. It is used by several of the top web browsers, operating systems, mobile phones, and other embedded systems.

SQLite is an embedded SQL database engine. A complete SQL database with multiple tables, indices, triggers, and views, is contained in a single disk file.

SQLite was designed to allow the program to be operated without installing a database management system or requiring a database administrator.

SQLite database files are a recommended storage format by the US Library of Congress. 

Richard Hipp designed SQLite in the spring of 2000. He is the primary author of SQLite as well as the Fossil SCM. He continues to serve as the project architect for the SQLite project.

SQLite implements most of the SQL-92 standard for SQL but lacks some features.

SQLite is open-source, not open-contribution. All of the code and documentation in SQLite has been dedicated to the public domain by the authors. Anyone is free to copy, modify, publish, use, compile, sell, or distribute the original SQLite code, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means. In order to keep SQLite in the public domain and ensure that the code does not become contaminated with proprietary or licensed content, the project does not accept patches from people who have not submitted an affidavit dedicating their contribution into the public domain. 

SQLite had a Code of Conduct adapted from The Rule of St. Benedict. It was renamed to "Code of Ethics".

There are over 600 lines of test code for every line of code in SQLite. Tests cover 100% of branches in the library.

The SQLite Consortium is a membership association dedicated to insuring the continuing vitality and independence of SQLite. 

LibSQL is an interesting fork of SQLite that is both open-source and open-contributions.