Some Open Development Environment (ODE) solutions require a specialized setup on the client machines. If you are simply serving maps, consider ArcIMS.
The only time an ODE solution warrants the effort of client setup is to provide capabilities that only ArcInfo has. In that case, the first suggestion is to write a Java application rather than an applet. The trouble of setting up a machine to run an ODE applet usually outweighs the benefit gained because the main goal of an applet is to avoid requiring end users to install anything.