I wonder what the legalities are with that shirt... I suspect that the JL8 artist is only allowed to do his thing because he hadn't been making any money from Warner Bros and DC Comics' licensed characters. (I wrote "hand't been" because he now has a Patreon account. I'm not sure how that work legally, either.) I am also guessing that the purveyor of the T-shirt is probably not that comic strip creator and might not have permission from either him or DC Comics to use these characters.