the dev for xnurbs quit the rhino forum due to all the backlash he received there. i don't think that many rhino users actually use xnurbs, from what i have read there. there is another plugin under dev that the users are clamoring for. basically, rhino is fine with third parties trying to fix all their geometry kernel deficiencies with plugins. which costs the users even more money. to me, the whole plugin thing is a joke, if they involve fixing core geometry deficiencies. other areas is a different story. like fea or cfd or something. plugins make sense in those cases. if you really want to use xnurbs then plasticity would be the way to go. much much cheaper.