/ducks
The only time I have seen a java applet recently was on a website with ATARI emulator (I guess it still wasn't ported to JavaScript and/or Flash).
...except that there are stock trading software that is written as java applets...sigh...
I know one person who calls it ECMAScript. You probably know an awful lot about this person just by my telling you that one thing.
Modern browsers implement ECMAScript 5; older browsers and AS 2.0 implement ECMAScript 3. ECMAScript 4 was scrapped, but AS 3.0 still implements it. Wikipedia, as usual, has all the gory details if anyone is actually interested http://en.wikipedia.org/wiki/ECMAScript
Browsers all implement HTML differently, but we're happy to refer to it by the name of the standard.
mocha and livescript were the names at netscape. naming it javascript was a marketing strategy and a product of the sun-netscape cooperation. the ecmascript standard was born later, after the adoption of javascript/jscript.
Supersets, not subsets. In terms of syntax, there is essentially no difference between ECMAScript, JavaScript, and JScript. They're just different implementations of the same thing. In fact, the only reason JScript has a different name is because Microsoft didn't want to license the Java trademark from Sun.
ActionScript is a different animal; it's a superset of ECMAScript and has a lot of additional syntax features, like data type support.
In any case, to work across different browsers, JS code is usually written in the intersection of the ECMAScript superset languages implemented by those browsers. That intersection is ECMAScript.
I'm curious who owns the LiveScript trademark, if anyone. If the Mozilla Foundation inherited it from Netscape/AOL, they should give it to ECMA. At this point, the association with Java is probably more of a negative.
(The most popular web browser can't even use the JavaScript trademark, due to totally unrelated events from 15 years ago. IMO a rebranding would still be feasible.)