What it is: An open-source database engine based on InterBase.
Where you can find it: http://www.firebirdsql.org/
Runs on: MicrosoftWindows, LinuxOs, SunSolaris, MacOsx (Darwin), FreeBsd and OpenBsd, HpuxOs and AIX.
Supports Transactions in Delphi. -- Maciej Szumocki
How it differs from InterBase: Better support, good documentation, and very responsive developer team.
What it's not: An open-source browser that's now called MozillaFirefox.
I'm somewhat fuzzy on the distinction between a database engine and a database package like MySQL. Is Firebird meant to be embedded into applications like the old Jet and Foxpro DB engines were?
You can embed it into your application or run it as a server. I haven't used it for a long time but I remember it was pretty nice. -- TimJarmanCategoryDatabase