Someone else asked about this not too long ago, but I can't seem to
locate the reference. In any case, I have no immediate plans to
produce such a translator.
Davide
So there are a number of possibilities which makes be curious about you are interested in having the functionality in MathJax. I gather you are publishing in MathML and want your users to be able to copy and paste as LaTeX? That is a little unusual, in my experience, so anything you can share about the context of your project would be interesting.
--Robert