activeTAPI for Dynamics 365 and activeTAPI-Service use the activeTAPI REST service that is hosted on Microsoft Azure. The activeTAPI REST Service is an Azure Resource which is available for free to everyone who wants to use it.
However, shared usage is restricted to
These numbers are counted on the shared license. The more companies use the shared license the faster the service will reach its license limit. So, if you get a license exception while using the service, probably too many companies are using the service at the same time.
If you enjoy the service and if you want to have your own license, well, just get you own dedicated license.