H2 Database - H2 is free SQL database written in Java
4D - 4D is a relational database management system and IDE.
MySQL Workbench - MySQL Workbench is a unified visual tool for database architects, developers, and DBAs.
LiveCode Platform - It is Both Under the GPL and it is also Proprietary if using the GPL version the software you make...
PostgreSQL - PostgreSQL is a powerful, open source object-relational database system.
Amazon RDS - Easy to manage relational databases optimized for total cost of ownership.