>> "Do you have any plans to deal with this situation, which is becoming more common? "
Yep, before the end of this year we have a hosted version of the TurboFloat Server instance planned. You or your customers will be able to "spin up" and instance of the TurboFloat Server hosted on our infrastructure. They'll also be able to manage it and view everything about it directly in the upcoming customer portal.
The price is cheap (cheaper than creating a VM instance on AWS, Linode, Azure, etc., etc.) and it has the added benefits of (a) always having the latest backwards-compatible TurboFloat Server instance running and (b) having security (DDoS protection, latest updates, abuse monitoring, etc.).
>> "Would it be possible, for example, to check if an activated TFS key is being used simultaneously on different IP addresses?"
IP addresses aren't a useful indicator of anything. That's why we completely ignore them except for display and informational purposes in LimeLM. See: https://wyday.com/limelm/features/why/#wrong-id