No, no subscription will be made when purchasing TAPICall.
TAPICall is always prepaid for 2 years.

No, TAPICall is not a TAPI driver.
TAPICall is a CTI- software which needs a TAPI- driver to work. Alternatively, TAPICall can be connected directly to a FRITZ!Box, but you do NOT receive a driver, but the option to make and evaluate calls via TAPICall.

This behavior is often the case. After a Windows-update, Microsoft restores many services to a default value. This also applies to the "Telephony“" service, which is essential for all TAPI- drivers. Open the services in Windows, there select the service “Telephony“. After right-clicking, select "Properties“". Now set the start type to automatic, then confirm this entry with "Apply“. Restart the computer now.

An Exchange server is suitable for this purpose.
There you create a public contacts-folder and grant access to all employees. If you don't want to run a local Exchange-Server, you can alternatively use the Online Exchange from Microsoft.

Yes, TAPICall can also be installed on a terminal server.
For each session to get a valid license, a few adjustments are necessary. These are in our Terminal Server Guidelines described.