LibreOffice - Base - Base, database, database frontend, LibreOffice, ODF, Open Standards, SQL, ODBC
4D - 4D is a relational database management system and IDE.
My Visual Database - Using My Visual Database, you can create databases for invoicing, inventory, CRM, or any specific purpose.
LiveCode Platform - It is Both Under the GPL and it is also Proprietary if using the GPL version the software you make...
MongoDB - MongoDB (from "humongous") is a scalable, high-performance NoSQL database.
Amazon RDS - Easy to manage relational databases optimized for total cost of ownership.