IIRC you can run 25 instances on 1 node, so that would be active / passive, if it is licensed accordingly
If you want to run 1 instance on Node1 and 1 instance on Node2, then you will need to purchase licenses for the second node.
As with anything licensing, speak to MS or your MS Reseller, dont take the public forum as the truth, you best get it in writing from the people who make the rules.