I find it to be an interesting philosophical question about what defines a language.
If you write code in Java, but compile it to native format (using gcj, for instance) instead of using the JVM, is it still Java? In doing so, you lose what is probably the language's biggest selling feature.
Or, perhaps less relevant now, but I remember the days where people would go on about how Ruby didn't support native threads. Except there were interpreters that did use native threads with the exact same Ruby code. Was Ruby code running under one of those other interpreters still a Ruby application?
PHP too comes with expectations about the environment, like how it integrates into the web server stack, which if not met, is it still PHP? I'm not really familiar with HipHop, but, for instance, if you have to compile your code before deployment, you're not meeting one very prominent expectation of PHP: The ability to edit the code in-place on the live server (best practices notwithstanding).
So, what does define a language? Is a language just the syntax? Standard library APIs? Standard library behaviour (see Ruby example)? Runtime environment? I'm not sure you will find a generally accepted answer.
There used to be a generally accepted answer, which is that there were languages, and there were implementations of languages, and that those were separate things. C++ was not g++, and vice versa.
But the lines got very much blurred by the rise of scripting languages, in which - typically - the language was defined by the implementation. So for a few years there, it really was difficult to tell whether this was Python or CPython.
Fortunately, nearly all the languages to which this applies matured and got new implementations. Rubyists often to refer to the C ruby implementation as MRI (Matz' ruby interpreter), and there are lots of different Ruby implementations now. Python went out of its way to document behaviour which was specific to CPython, and put a lot of weight behind Unladen Swallow and Pypy.
But your Java example is bonkers. Compiling Java to native is still Java, its just not JVM. Compiling clojure to JVM is just JVM. The language feature is not the language. In Java's case, the language is specified, the VM is specified, the bytecode is specified. There really should be no ambiguity at all there.
If you write code in Java, but compile it to native format (using gcj, for instance) instead of using the JVM, is it still Java? In doing so, you lose what is probably the language's biggest selling feature.
Or, perhaps less relevant now, but I remember the days where people would go on about how Ruby didn't support native threads. Except there were interpreters that did use native threads with the exact same Ruby code. Was Ruby code running under one of those other interpreters still a Ruby application?
PHP too comes with expectations about the environment, like how it integrates into the web server stack, which if not met, is it still PHP? I'm not really familiar with HipHop, but, for instance, if you have to compile your code before deployment, you're not meeting one very prominent expectation of PHP: The ability to edit the code in-place on the live server (best practices notwithstanding).
So, what does define a language? Is a language just the syntax? Standard library APIs? Standard library behaviour (see Ruby example)? Runtime environment? I'm not sure you will find a generally accepted answer.