Oracle SQL Developer and PostgreSQL

Oracle SQL Developer 4.0.1.14 surely does support connections to PostgreSQL.

• download JDBC driver for Postgres (http://jdbc.postgresql.org/download.html)
• in SQL Developer go to Tools → Preferences, Database → Third Party JDBC Drivers and add the jar file (see http://www.oracle.com/technetwork/products/migration/jdbc-migration-1923524.html for step by step example)
• now just make a new Database Connection and instead of Oracle, select PostgreSQL tab

Edit:

If you have different user name and database name, one should specify in hostname: hostname/database? (do not forget ?) or hostname:port/database?.

(thanks to @kinkajou and @Kloe2378231; more details on https://stackoverflow.com/a/28671213/565525).