Licenses purchased from www.redshift3d.com are permanent which means they are not a subscription. Furthermore, these licenses work on all supported 3d apps.
Since Redshift was acquired by Maxon in 2019, Maxon introduced a Cinema4D+Redshift subscription bundle option specifically for Cinema4D users. These subscription licenses can be purchased from Maxon's website: https://www.maxon.net/en-us/buy/. Please note that these subscription licenses work only for Cinema4D.