Firebird. Management tools: IBExpert Personal Edition en FlameRobin

PostgreSQL (released under the BSD license).
MySQL, Drizzle, MariaDB, Percona Server, OurDelta
MySQL vs PostgreSQL
phpPgAdmin voor web-based PostgreSQL beheer.
phpMyAdmin voor web-based MySQL beheer.
SQL Buddy – Web based MySQL administration

DBComparer
DBComparer sourceforge project for predecessor or other compare tool.