No launcher. No web browser plug-in. Working Quake3: CPMA port to web based environment is up and running. Notes from the author:
QuakeJS is a port of ioquake3 to JavaScript with the help of Emscripten.
This project started to demonstrate the feasibility of browser-based gaming, and what better way than with a classic game whose core gameplay revolves around the kind of responsive APIs that are available with HTML5 today.
Try it out at: http://www.quakejs.com/