I'm fairly sure that languages cannot ever be copyrighted, programming or otherwise.
(Such an interpreter would likely contain a table of function names. The effect of this ruling is to clarify that that set of function names can't be copyrighted, so the alternative implementation of your interpreter can copy it. We already knew that the names themselves couldn't be copyrighted, but this ruling clarifies that also the "structure, sequence and organsiation" of those function names can't be copyrighted either.)
But yes, the underlying implementation is still subject to copyright (and potentially, patent). You can't copyright the fact that your scripting language has an operator spelled >< that concatenates strings, but you can copyright your particular code that performs string concatenation.