I don't think they're litigious at all really. When you think of the ideas, races, mythology that was first articulated by the LoTR books which have been ripped off hundreds of times since. Big companies raking it in off direct LoTR spinoff is meat and drink to US copyright lawyers. I suspect the estate of JRRT are just being well advised. The funniest posts I saw after the Fellowship was first released were the complaints that it was derivative.