JCAPS stands for Java Composite Application Platform Suite. It's not an application server, but a set of tools covering several development targets. Some of the domains that are covered include data transformation (eGate), business process management (eInsight), B2B transaction management (eXchange Integrator), and so on.
Previous releases of these tools have been around for some time under different names. Sun Microsystems bought the founding company (SeeBeyond Technology) a while back and has since been re-packaging many of these tools to use well-known standards (J2EE, Web Services, etc.) and message protocols (HIPAA, EDIFACT, ebXML, etc).
The software release happens to include an Integration Server, which in the current releases is a modified Sun Java Application Server, Platform edition component. The toolset also includes a design tool (based on NetBeans) and a management server with a browser-based interface.
Make visible what, without you, might perhaps never have been seen. - Robert Bresson
JCAPS is a freeware till production env. In case you are using JCAPS for production/live we need to purchase the license from Oracle (formerly SUN). There is not direct download link for JCAPS but you can contact the sun support site for more details.