I would prefer not to use the term “legacy” in this context. I’ve been trying for some time to convince a government agency to move away from their current legacy system (dating back to the Windows 3.1 era) to a modern platform like AwareIM. Referring to the new model as “legacy” again doesn’t help that effort.
It would be clearer to distinguish between two types of licensing models:
1) Server-based licenses
2) Subscription-based licenses
Additionally, I believe that in a subscription model, the number of servers should not influence the cost. I use additional servers not because of scaling client numbers, but to ensure performance remains acceptable and to reduce the risk of downtime if one server crashes.