PostgreSQL is released under the
PostgreSQL License, a liberal Open Source license, similar to the BSD or MIT licenses.
Originally PostgreSQL was released under a license similar to, but not identical with, the BSD license. However in 2009 RedHat decided to label it as a MIT license , which it is also not, and controversy ensued. The issue was resolved by applying to the Open Source Initiative (OSI) for recognition of the existing
PostgreSQL License as a separate license, which was granted in 2010 .
Some other PostgreSQL projects such as
pgAdmin are also released under the
-  https://www.redhat.com/archives/fedora-legal-list/2009-August/msg00031.html
-  http://www.crynwr.com/cgi-bin/ezmlm-cgi?17:mmp:969
-  https://pgsnake.blogspot.com/2010/02/postgresql-now-with-added-open-source.html