Firebird is a relational database offering many ANSI SQL standard features that runs on Linux, Windows, MacOS and a variety of Unix platforms. Firebird offers excellent concurrency, high performance, and powerful language support for stored procedures and triggers. It has been used in production systems, under a variety of names, since 1981.
The Firebird Project is a commercially independent project of C/C++ programmers, technical advisors and supporters developing and enhancing a multi-platform relational database management system based on the source code released by Inprise Corporation on 25 July, 2000.
The source code is released under variants of the Mozilla Public Licence 1.1 (MPL):
The source code can be found at:
https://github.com/FirebirdSQL/firebird
Build instructions are here: https://www.firebirdsql.org/en/building-the-code/
Bugs and feature requests should be submitted at:
https://github.com/FirebirdSQL/firebird/issues
You may find more details at:
https://www.firebirdsql.org/en/development/