offbrands are 100% legal as you cannot copyright a "species".
offbrands of any form are never illegal unless they take a trademarked name and use it for commercial profit, not counting "virtual currency" like dA points. off-branders do not typically use the name of the species they're offbranding.
in addition, most species names are not trademarked. the only trademarked species names i know of are sushi dogs and cinnadogs, but that still does not stop anyone from making their own character of the species so long as they don't sell it with the name attached.
if you ask any serious species owner (ex. one who has trademarked their name), they will tell you the same thing.
creating a species and claiming it to be "closed" does not actually have any sort of legal value.