I did wonder if they were aliens, but I don't really remember there being anything to indicate they weren't just another group of humans from somewhere else in The J.
The implication was that they were aliens. The collector also said that the "mossipedes" were used as guard animals by "the indigenous people" of some planet he'd visited, which would pretty much have to be sentient aliens, unless he was misusing the word "indigenous" -- and since this script included such vocabulary-boosters as "gynoid" and "afferent teleplasticity," I doubt it would've misused that word.
So yes, I think we are getting indications that this is not a humans-only universe. In fact, we may have seen an alien creature of a sort other than "Mossy" -- that giant-spider thing that Dutch accidentally "keyed" into the molecular printer. Which could've been some kind of bioengineered organism, or maybe not.