4D - 4D is a relational database management system and IDE.
LiveCode Platform - It is Both Under the GPL and it is also Proprietary if using the GPL version the software you make...
Amazon RDS - Easy to manage relational databases optimized for total cost of ownership.
Informix - IBM Informix is a secure embeddable database optimized for OLTP and IoT data. Informix can seamlessly integrate SQL, NoSQL/JSON, and time series and spatial data.
H2 Database - H2 is free SQL database written in Java
ApexSQL - ApexSQL is a complete suite of tools intended for SQL servers for DBAs and developers that streamlines and automates SQL Server database management and development processes.