RealMint is a telnet client and terminal emulator written completely in JavaScript. It connects to your telnet server through an HTTPS tunnel, so as long as you have a web server that supports JSP (the only tunnel backend available at the moment), and a telnet daemon (listening on localhost) you need only copy the RealMint files onto your server and navigate to them in your browser.
Unlike most other web-based shell access programs which implement the terminal emulator on the server side, sending entire screen updates to the client, RealMint implements the terminal emulator in the browser on the client side; RealMint's server side code consists only of HTTPS tunnel support written in an interpreted language (Java).