• Apache CassandradatabasesActiveApache-2.02026-07-05Apache Software Foundation — Distributed wide-column database designed for fault tolerance with no single point of failure, born at Facebook from Amazon's Dynamo and Google's Bigtable ideas and donated to the Apache Software Foundation in 2009.
• ClickHousedatabasesActiveApache-2.02026-07-05ClickHouse contributors — Column-oriented database for real-time analytics, open-sourced by Yandex in 2016, that aggregates billions of rows per second on ordinary hardware. Its release set a new public baseline for analytical performance.
• DuckDBdatabasesActiveMIT2026-07-05DuckDB Foundation — In-process analytical database — the "SQLite of analytics" — running complex column-store queries inside your application or notebook with zero setup. Developed at CWI Amsterdam, the birthplace of much database research.
• MariaDB ServerdatabasesActiveGPL-2.0-only2026-07-02MariaDB Foundation — Community-developed relational database created by MySQL's original authors on the day Oracle acquired Sun, precisely to keep the codebase free forever. Drop-in compatible with MySQL and the default database of most Linux distributions.
• PostgreSQLdatabasesActivePostgreSQL License2026-07-02PostgreSQL Global Development Group — Advanced open source relational database with a lineage reaching back to the POSTGRES project at UC Berkeley in the 1980s. Renowned for standards compliance, extensibility and transactional integrity, it is the database on which much of the modern internet quietly runs.
• SQLitedatabasesActivePublic Domain2026-07-02D. Richard Hipp & SQLite team — Self-contained, serverless SQL database engine — a single small library that is likely the most widely deployed database in the world, embedded in every browser, phone and countless applications. Its public-domain code and decades-long stability guarantee make it a model of software meant to last.
• ValkeydatabasesActiveBSD-3-Clause2026-07-05Linux Foundation community — High-performance in-memory key-value store forked from Redis under the Linux Foundation when Redis abandoned its open source licence in 2024 — the community and major cloud providers moving as one to keep the software free.