I'm actually quite curious: exactly what rights do you claim that you have to that piece?
I am not a lawyer, but my understanding is that game mechanics are not protected by copyright (at least in the US). Furthermore, 'like a Queen but 3 spaces at most' is a trivial and obvious variation on a well-known piece; it has probably been independently invented thousands of times, all over the world, long before Dragonchess showed up.
You're also not the first people to give the name 'dragon' to a chess piece, though you might be the first ones with that exact name/movement combination.
So what precisely is it that you claim is protected, and what rights do you assert over it?