The term 'justified', I presume, is an evaluative term, a term of appraisal. Any correct definition or synonym of it would also feature evaluative terms. I assume that such definitions or synonyms might be given, but I am not interested in them. I want a set of substantive conditions that specify when a belief is justified. Compare the moral term 'right'. This might be defined in other ethical terms or phrases, a task appropriate to metaethics. The task of normative ethics, by contrast, is to state substantive conditions for the rightness of actions. Normative ethics tries to specify non-ethical conditions that determine when an action is right. A familiar example is act-utilitarianism, which says an action is right if and only if it produces, or would produce, at least as much net happiness as any alternative open to the agent. These necessary and sufficient conditions clearly involve no ethical notions. Analogously, I want a theory of justified belief to specify in non-epistemic terms when a belief is justified. This is not the only kind of theory of justifiedness one might seek, but it is one important kind of theory and the kind sought here.
I am not sure I feel the motivation for this constraint. I can certainly see why we might not be satisfied by a theory of justification that is circular (justification is justification) or otherwise uninformative (justified belief is belief that is epistemically good), but barring all epistemic notions from the right-hand-side seems like a pretty strong constraint. But perhaps I've misunderstood Goldman's motivation here? Is the naturalistic reduction constraint motivated by something other than informativeness?