I am looking into the licensing of SQL Server 2012 when using Always on with 2 servers.
It is not clear to me if Always On is only available as Active/Active and not Active/Passive.
For reference I found a couple paragraphs in the SQL Server 2012 Licensing Reference Guide but it doesn't mention passive servers with respect to Always On.
Licensing SQL Server for High Availability SQL Server software can be configured so that if one server fails, its processing will be picked up, recovered and continued by another server. All editions of SQL Server 2012 provide basic high availability features including backup log shipping, database mirroring and two-node failover clustering. Advanced (AlwaysOn) high availability features in SQL Server 2012 Enterprise Edition include enhanced support for multiple, active (readable) secondary servers and support for multi-site failover clustering. Log shipping and database mirroring take place at the database level, whereas failover clustering takes place at the SQL Server instance level.
AlwaysOn Availability Groups New for the SQL Server 2012 Enterprise Edition, AlwaysOn Availability Groups enable customers to configure multiple databases that will failover as a unit, with support for up to four active secondary servers and two synchronous secondary servers. The ability to use secondary servers for more than just passive failover support can improve the performance of primary, reporting and backup workloads due to better balancing of workloads across instances, helping to provide better return on hardware investment. Note: When secondary servers are actively used to support these additional workload scenarios—that is, when the servers used for failover purposes are no longer truly passive—they must be fully licensed accordingly.