100 Open Source replacements for expensive software

Firebird is listed in the “100 Open Source Replacements for Expensive Applications” article:

31. Firebird

Replaces Microsoft SQL Server Standard ($899 and up)

Under development for more than three decades, Firebird is a relational database that boasts “excellent concurrency, high performance, and powerful language support for stored procedures and triggers.” Paid support is available through third-party providers. Operating System: Windows, Linux, Unix, OS X, Solaris