Databases

---

• SQLite   
  SQLite is a small C library that implements a self-contained, embeddable, zero-configuration SQL database engine. [Windows, Linux] (C language) Open Source, Public Domain
  
  http://www.sqlite.org/

---

• Firebird   
  Firebird is a relational database offering many ANSI SQL-99 features that runs on Linux, Windows, and a variety of Unix platforms. (C, C++) Initial Developer's Public License. (IDPL) and InterBase Public License v.1.0
  
  http://firebird.sourceforge.net/

---

• MySQL   
  The world's most popular open source database. (Linux, Windows) GNU License
  
  http://www.mysql.com/

---

• PostgreSQL   
  PostgreSQL is a highly scalable, SQL compliant, open source object-relational database management system. (Linux, Windows) [C] BSD license.
  
  http://www.postgresql.org/

---

• MaxDB   
  MaxDB is a heavy-duty, SAP-certified open source database for OLTP and OLAP usage. [All enterprise HW/OS platforms] Commercial License or Open Source, GPL
  
  http://www.mysql.com/products/maxdb/

---

• GNU SQL Server   
  SQL Server is a free portable multiuser relatational database management system. It supports the full SQL89 dialect and has some extensions from SQL92. It provides multiuser access and transaction isolation based on predicative locks. [UNIX] (C) GNU
  
  http://www.ispras.ru/~gsql/

---

• Berkeley DB Database   
  Sleepycat Software makes the Berkeley DB database, Berkeley DB XML and Berkeley DB Java Edition.
  
  http://www.sleepycat.com/

---