Nope, there are no card limits. (Except for the Agenda limit in the Corp deck, there are no deck design limits of any kind.)
This was a reaction by Richard Garfield to a design mistake in Magic. Originally he thought rarity alone would keep powerful cards balanced, not anticipating the way the collector market would grow. WotC shortly learned that rarity was irrelevant for this; powerful cards also needed to be high-cost.
In the next two games, Jyhad and NetRunner, the design team tried to make sure that every card was costed correctly and not game-breaking even en masse. So neither game had a card limit.
(They didn't always do a perfect job, so some tournaments impose card limits, but the game rules don't.)