Hi,
You can use active-active fail-over as long as you have the same license (or no license) on both FWSMs. Out-of-the-box you get 2 contexts + admin (which can also be used a filtering context).
You can issue
fwsm# sh activation-key
... you should have something similar:
Failover : Active/Active
........
Security Contexts : 2
Traian