Only the tree owner can download a GEDCOM of a tree, altho anyone else can click thru an entire tree and copy it to theirs with no trouble; which kinda defeats the purpose of not allowing anyone but tree owners to download GEDCOMS of their trees.
Ancestry needs to put up a notice:
"Attention Tree Owners- we will not let anyone but you download a GEDCOM of your tree, but we will provide tools so that anyone can copy all your information directly to their trees".
If they were that upfront about it you'd hear screams of outrage from here to Mars and back.
But, of course, they aren't; they bury it in legal mumbo-jumbo and hope most users won't pay attention.