Netscape created a language which they called LiveScript when it first shipped in a beta build, largely influenced by Java. By the time of Netscape Navigator 2.0 beta 3, they had negotiated a license for the Java name from Sun and renamed the language JavaScript (and, as wamatt pointed out, Sun owned the JavaScript trademark, now owned by Oracle following the Sun acquisition).
IE3 shipped a reverse-engineered copy of JavaScript, which they called JScript because they didn't have a license to the JavaScript trademark.
Later in the same year that Netscape Navigator 2.0 and IE3 shipped, Netscape submitted a specification of their JavaScript language to Ecma. What followed, as far as I'm aware, was a bit of a debate about naming: JavaScript was basically out of the question due to it being a Sun trademark, JScript was a MS term that Netscape didn't want to legitimise, and hence the compromise was ECMAScript (why this uses the pre-1994 capitalisation of Ecma is a good question!).
So, essentially, JavaScript, JScript, and ECMAScript are three names for the same language.
This then gets a bit complicated as Netscape and then Mozilla referred to ECMAScript revisions as JavaScript versions, and then started adding non-standard extensions as new JavaScript versions, though they've basically killed that now.
> So, essentially, JavaScript, JScript, and ECMAScript are three names for the same language.
This is a little wrong/misleading.
ECMAScript is the specification; JavaScript, JScript, and ActionScript, are various implementations of the specification. Each implementation provides additional features not described in ECMA specs, such as access to ActiveX and the local computer in JScript.
Mozilla's view is that JavaScript is a language, of which they provide two implementations: SpiderMonkey and Rhino.[1]
As far as I'm aware, MS has used JScript to use to both their original implementation and the language it implements, as well as JScript.Net being both the implementation and the language it implements. I can't find any citation for this, however.
Adobe considers ActionScript a language, with implementations including AVM.[2]
[Edit:] I just realised you could also potentially mean "implementation" insofar as they define a host environment for ECMAScript, except JavaScript especially does not: just look at the difference between SpiderMonkey-in-a-browser and SpiderMonkey-on-the-CLI.
I believe that's backwards. Javascript was based on Scheme & Self, the Java resemblance is only superficial; added later for marketing purposes when they picked up the JavaScript name.
The syntax was largely influenced by Java, although Scheme & Self influenced more of the semantics than Java did. From memory of what Brendan has written before, the language was meant to be, per managerial plans, "Java but a scripting language".
The syntax sure is much closer to Java than Scheme or Self. So was the obscuring of prototypal inheritance with the new keyword along with the Math object.
Netscape created a language which they called LiveScript when it first shipped in a beta build, largely influenced by Java. By the time of Netscape Navigator 2.0 beta 3, they had negotiated a license for the Java name from Sun and renamed the language JavaScript (and, as wamatt pointed out, Sun owned the JavaScript trademark, now owned by Oracle following the Sun acquisition).
IE3 shipped a reverse-engineered copy of JavaScript, which they called JScript because they didn't have a license to the JavaScript trademark.
Later in the same year that Netscape Navigator 2.0 and IE3 shipped, Netscape submitted a specification of their JavaScript language to Ecma. What followed, as far as I'm aware, was a bit of a debate about naming: JavaScript was basically out of the question due to it being a Sun trademark, JScript was a MS term that Netscape didn't want to legitimise, and hence the compromise was ECMAScript (why this uses the pre-1994 capitalisation of Ecma is a good question!).
So, essentially, JavaScript, JScript, and ECMAScript are three names for the same language.
This then gets a bit complicated as Netscape and then Mozilla referred to ECMAScript revisions as JavaScript versions, and then started adding non-standard extensions as new JavaScript versions, though they've basically killed that now.