...but desires primarily to calculate digits of pi? ...but desires primarily to paint waterlilies? ...but desires primarily to randomly reassign its primary desire every year and a day? ...but accidentally desires primarily to serve humans?

I'm having difficulty determining which part of this scenario you think has ethical relevance. ETA: Also, I'm not clear if you are dividing all acts into ethical vs. unethical, or if you are allowing a category "not unethical".