PostgreSQL is one of the most widely used relational database management systems today. It is object oriented, it is multisystem, so you can use it on any operating system and under a free license.

It has been developed since 1996 by a community of developers (not a company or foundation) based on DBMS POSGRES, which emerged (like many other technologies) from a US military research project (DARPA, ARO) with civilian participation.