Apache Pluto is a subproject of the Apache Portals Project. The current stable release of Apache Pluto is version 3.0.0. Pluto 3.0 provides the reference implementation and technology compliance kit for JSR 362 Portlet Spcification 3.0. It complies to the JSR 362 and JSR 286 standards.
Pluto 2.0 is the current trunk of development and has an active development community. Version 2.0 has a new architecture and is a rewrite of the Pluto 1.1 code-base. Pluto 2.0 is the reference implementation of version 2.0 of the Java Portlet API specification (JSR-286). The JSR-286 specification adds interportlet coordination (events and shared render parameters), portlet filters and resource serving to the Portlet API in addition to numerous other changes from version 1.0. However, Pluto 2.0 is also fully compliant to the 1.0 Portlet Specification. Pluto 2.0, like Pluto 1.0.1, but unlike Pluto 1.1, runs inside the Jetspeed portal. Pluto 2.0 is embedded in Jetspeed 2.2.x versions, whereas Pluto 1.0.1 is embedded in Jetspeed 2.1.x versions.
Pluto 1.1 introduced a new container architecture from version 1.0.1. If you are embedding Pluto in your portal, realize that 1.1 is not binary compatible with Pluto 1.0.x. Pluto 1.1 is no longer actively developed. Version 1.1 is only maintained for bug fixes in dependent portals.
Pluto 1.0.1 was the first stable release of Pluto. This version of Pluto is utilized as the portlet container for Jetspeed and other portals. In addition, Pluto 1.0.1 is embeded within Apache Geronimo. Pluto 1.0.1 is no longer activily developed. 1.0.1 is only maintained for bug fixes in portals such as Jetspeed 2.1.x.