Most of our ISA filter customers will one day decommission their ISA servers and move to the TMG platform. This article talks about our licensing costs for TMG filters.
ISA filters and TMG filters are separate products
Unlike moving from ISA 2004 to ISA 2006, TMG is an incompatible platform requiring different filters. So, for example, Captivate for TMG cannot use the same license as Captivate for ISA. This means to use Captivate for TMG you have to buy the TMG license, even if (at one time in the past) you bought an ISA license.
What if I won't be using my ISA filter licenses any more
Even if you are decommissioning your ISA servers, you can't use those licenses for TMG. This sounds like a mean thing to do, but there is actually a very simple reason why we have to do it:
Unlike other companies, we sell software licenses as a one time cost. We never charge any annual recurring cost or maintenance to keep a license "current". And just like you, most of our TMG users are simply upgrading from ISA. Therefore, the only way we can defray the cost of supporting our products on the TMG platform is to charge customers (one time) when they need to buy the filter for TMG. Otherwise we would net zero dollars for TMG filters, and have no motive to support it.
We hope that makes sense. We are not trying to be greedy, but just support the filter development cost on this platform.