I think if there was a lawsuit, it would have happened already seeing how the letter is dated with a deadline back in April 2009.
I really don't get why there are still people asking for AJR's reply, when they have already made several replies on forums like fitfreak stating their stance in this, which pretty much summarizes to their parts being supplied only from J's racing. Now why are they not posting here too I have no clue, maybe they can really care less about revscene