No, it's not. In this case, abuse is about intent: DOS intends to cause distress, losses and denial of service to others. Use with third party apps without adds intends none of this: the intent is to use something else to access the service in an otherwise normal (to the user) way.

Arguably third-party apps that are scrapers are somewhere in between these two in acceptability, but that's a question of "are scrapers morally fine and should they be legally allowed", not a question of whether third party clients are to be allowed at all.