For the applet, what must be installed on web client machines?
No special Jmol-specific software needs to be installed on the client machines. Client machines do not need anything other than a web browser that supports Java, and a recent version of Java installed and enabled in the browser (best is Java Virtual Machine from Sun). When a client visits a web page containing the JmolApplet, the applet gets automatically downloaded from the web server and executed. The JmolApplet runs as an untrusted applet. The applet does not any confirmation from the user to load and begin execution. There is also a trusted version of the applet (JmolAppletSigned) for authors that prefer to make use of its advantages (see TechNotes, Browser Enhancement Technologies for details). Jmol.js JavaScript Library It is strongly recommended that you use the Jmol.js JavaScript Library to allocate your applets within your web pages.