To clarify adrian's post, the B7 airbag is a dual stage airbag with two electrical connectors. The dual stage airbag allows for a softer deployment in less severe collisions by deploying only one explosive. For more severe collisions, both explosives are deployed.
In theory, to use this with an older single stage airbag control unit (as in a B6) you just need to connect both sockets on the B7 airbag to the single pair of electrical contacts. This will allow the dual stage airbag to fully deploy when instructed to by the single stage airbag control unit.
Of course, it is up to the owner whether or not to take the responsibility of altering your vehicle's airbag electronic system.