Here are the reasons Firebird is preferred over SQL Server and Oracle Express | #SQLServer #Oracle #MySql

Here are the reasons Firebird is preferred over SQL Server and Oracle Express : No license fees and is Limitless (No matter how large is the machine CPUs+ Memory or how big is your database :Terabytes) .
Start small grow large and still no fee to pay and you can use the same database file :example.fdb in both embedded and in SuperServer version (client server model) after application requires external connection (Did i mentioned that is multi threaded and lockless if you compare it with sqlite )

http://blog.cincura.net/231742-firebird-embedded-in-comparison-to-sql-server-compact-edition-4/

Here are other discussions on what Firebird advantages are over other Open Source Relational Databases

Here are the reasons for Choosing Firebird over Mysql
http://blog.marcocantu.com/blog/mysql_interbase_firebird.html

Also Firebird is NOT scamware like Oracle with mysql you can actually make live backups and not like in innodb engine case where you need to pay for the live backup tools