The f* did I just read? I hate to slander other softwares but if you want to see ridiculous license terms and pricing go over to IPB. If you don't maintain your $250/6 mo you'll be completely blocked out of the community forums and marketplace, as well as (obviously) their support. No updates at all, including security updates.
You didn't purchase the software, you got a license with terms that it can be used on one site.
I mean, security updates are always free. What more do you want? Using one license on multiple sites is both an insult to XenForo (and its developers), personally my favourite forum software on the market regardless of the price tag, and everyone who has paid additionally for more licenses.
The fact that you can still post in the community is an example of how legitimate the pricing structure is here. You still have complete community forum access. Good luck getting that at some other competitors.
The software is so powerful that you can make something else out of it, completely different from a forum. It's got a good, strong, extensible code base.
XenForo is too cheap, if anything. I'm fine with their pricing if it means I can get good software for $140/license with $40/yr renewal.