No! The current plan is to launch the same way a mobile game would, with the app living on the device that purchased it. This has some pros and cons, of course. For example, you won't have to log into anything, it'll just live on your device and there's no barrier between you and the content. But this also means that it cannot be used on another device without another purchase.
While this will likely be the case at launch, we plan to flip this to a login at a later date so you can access it across devices, only needing a one-time purchase. THERE ARE NO PLANS TO REQUIRE A SUBSCRIPTION. We believe that you should own what you buy.