xmlrpc-c is a programming library for writing an XML-RPC server or client in C or C++. XML-RPC is a standard network protocol to allow a client program to make a simple remote procedure call (RPC) type request of a server. It's like SOAP or CORBA, but much simpler. This library speaks the same XML-RPC as similar libraries for lots of other programming languages, with most of the popular extensions. The client library uses either w3c libwww or Curl for HTTP. The server library contains a complete lightweight HTTP (Web) server and also facilities for running with CGI under any Web server.
The Application Switch sits between applications and service providers, allowing a central location for configuration instead of requiring the user to configure each application separately. The switch also allows mutliple services to be combined and appear as a single service to applications.
OpenEJB is a simple, lightweight Enterprise JavaBeans (EJB) container and server. You can embed OpenEJB in your own applications, or in a Web application server like Tomcat, or run it as a standalone EJB server. It supports EJB 3.0, 2.1, 2.0, and 1.1, and has partial support for EJB 3.1.