For remote tag history providers I don't have to license the local gateway's tag historian module if the central gateway is activated, correct? I feel like this makes sense but want to verify as I haven't done a ton with tag historian specifically.
I'm pretty sure both ends need the license.
I think you need a licence for tag historian for the gateway to produce historian data and push them to db.
You can read historian from another gateway without the historian module if you use remote historian with GAN.
If you have the historian module you can directly query database and of course produce some historian data.