"without JVM" - providing what is necessary to run Java is a JVM in my book. That you compile Java to JavaScipt is just an implementation detail, isn't it? EDIT: Yeah, ok. It emphasises that you don't need an extra JVM on your computer.
"fully client side" - isn't that how Java Applets always have been executed?
"no plugins" - Not sure what you mean by "plugin". Installing an extension does not match that?
Hmm.. ok, ok I am nitpicking :)
Could you instead provide a bookmarklet that runs Java Applets on websites? That would be something I would use. I would not install an extension because I don't want your code to run outside of the browser sandbox.