GlassFish is a Java application server project created by Sun Microsystems that allows many developers to generate enterprise technologies that are convenient and scalable, as well as additional services that can be installed based on preference. It is a free, dual-licensed software under the GNU General Public License (GPL) and the Common Development and Distribution License (CDDL). GlassFish was acquired by Oracle in 2010.
Techopedia explains GlassFish
GlassFish was developed based on a source code that was released by Sun and Oracle’s TopLink persistence system. The project was launched in 2005 and the first version that supported Java EE 5 was released in 2006.
The reference implementation of Java EE is GlassFish, so it supports JMS, JavaServer Pages, Enterprise JavaBeans, RMI, JPA and servlets. Because of its nature, developers can create scalable and portable applications that easily integrate with legacy systems and technologies.