Do Availability Groups support Active/Passive?
If you are talking about AlwaysON Availability Group in that case as long as secondary replica(s) are used strictly for Disaster Recovery or StandBy database then you do not need to license those replica in terms of SQL Server Licensing. 

Few weeks ago, I had similar question related to AlwaysON availability group and here is the official answer I got from our MS Licensing Rep.

"When the secondary server does any work at all, like taking requests or running backups off of it, or any of the readable features of AlwaysOn are enabled then it must be fully licensed.

If its sole purpose of replica is for fail-over and none of the readable features of AlwaysOnare enabled, then the fail-over right provided below will cover that server from a licensing standpoint and a second license is not required."

In terms AlwaysON FCSI (failover clustering) licensing stays the same. You only license active node. If you use log shipping for DR you do not license your DR server. 

If you are in North America region, you can call Microsoft 1-800-426-9400, Monday through Friday, 6:00 A.M. to 6:00 P.M. (Pacific Time)   to confirm this.