Let me start by saying that Test Studio really shines with its record and playback ability so that, unlike QTP, you rarely have to deal with code at all. Our recorded steps work similar to a keyword driven test. Our test runner executes the specified action targeting the specified UI element all w/o a single line of code in the script. It's our record and playback ability that makes you much more productive.
Now to answer your question: no it makes no difference at all which language your test project uses. It will all get compiled into a DLL and the content of your DLL used during test execution. The Test Studio script will be used to directly drive the web browser and the DOM it contains, which is the HTML sent by the web application. Thus your test script won't even be able to get at code contained in your web application. This is why Test Studio can work with any web application regardless of the technology behind that web application (ASP.NET, jQuery, PHP, etc.). They all generate and send HTML to the browser and that's what Test Studio will see and work with.
I hope this helps.