You're making a worthless comparison.
You're making a worthless point. You're implying an entitlement to use someone else's work for free, and you disagree with the terms they set out to use their work. They're entitled to request any terms they want for you to use your work (within XenForo's resource guidelines when advertising here of course). It's up to you to decide whether those terms are acceptable to you or not.
But which if it does happen to do so, WILL be detected and that Dev will lose his privileges to post addons at xF dot com. It's happened before.
And I'm sure if the developer decides to use your data in a manner that isn't in compliance with their privacy policy and data protection law the same would happen. And on top of XF taking action, they'd be liable to action from a data protection authority. The consequences are more clear and worse. In the history of XF add-ons I do not recall a case where a developer had a data breach, or used data in an unauthorised manner. ******* would be the closest to it, and although I don't know the details of his case, afaik the issue with him didn't include that.
Your 'concerns' are ridiculous. You provide your email address to register on pretty much
any site. I have over 1000 accounts in my password manager, each of them with an email address of mine. It is the most basic requirement to create an account anywhere. I don't even trust half of those sites, and generally use a different email address to my personal for that. If you're still worried, you can use a throwaway disposable email address.
It's insulting to suggest that XenForo add-on developers are so irresponsible and incompetent that you're unwilling to trust them with
an (not necessary your main) email address, yet competent enough for you to use an add-on by them for free.
I don't. Never have, never will.
Then I don't understand your stake in this issue. You don't use those add-ons, great, so you have no problems here? Fantastic.