I'm glad I happened to have a look at this discussion. Particularly the point that the license can only be used for one domain. What if one wants to stop using Xenforo on the original domain, basically close the Forum and start a Forum on another domain? Can one move one's license from one domain that no longer has an instance of Xenforo on it to another domain, and, if yes, how does one do this - is there an application process involved?
I've done exactly that. In 2018 I started a forum on MindfulKindness that failed because people didn't want to post stories of such a personal nature. That hosting service was not renewed after a year and all the data simply went away. For this copy of XenForo, I paid full price.
Then this year I decided to try another forum on the technical theme of translating computer programs from one specific programming language to another. (My signature has the link.) For this forum I have numerous domain names pointing to it:
FoxProToCSharp
FoxToCSharp
VFPToCSharp
They all point to the same forum and content, which is an example for the original poster in this thread. For this issue of XenForo, I paid just the renewal price.
This second attempt is going slow, so I consider it a hobby for now. With GoDaddy hosting, nightly backups, security, email and forum software, it runs me about $20 US a month. Not bad for a hobby in my opinion. I use it to do my job at work and explore some of the graphics features of websites. I built my own graphics for the discussion balloons you see on my site and have dabbled with the main forum logo you see at the top, although I conceeded to a pro who helped me in the end w what you see at the top now.
The community support you can get here is nothing short of phenomenal. Some add ons are free, some cost. Got weekend ticket support here once while installing and appreciated that a lot.
Perhaps my third attempt will be the charm.
Good luck.