You can walk into any gun store and buy any rifle right now, including the AR-15 that is posted here. There is no liability for NYSpeed any more than there is for the gun store, buffalo news, or craigslist. Even the private seller can’t be held liable because NY has no requirements for a private seller to do a background check. If the seller is not liable there is even less responsibility on the advertising site.
There are no licensing laws regarding shotguns and rifles in NY.