Well that's my bad, but for what may be a good reason. Bill, as an active member and a current Diamond-level sponsor, you don't need to join, and you don't need to donate. So that page was blocked from the view of most sponsor levels. Now, the reason I did that is because way back when, we had a few members who donated, forgot they'd donated, and then donated again. And then they forgot they re-donated and donated again. Changing the permissions to block the page from view was an emergency stop-gap measure, and I guess I never came up with a good solution for what to do permanently. I've changed the permissions, allowing anyone can see the page, so the link is no longer broken.
Too in the weeds content below:
Because there are two different software systems running, one for the main site and one for the forum, I don't believe there's a way to set it such that, "If someone who's logged in to system B clicks on a link in system A, display this page. If someone who's not logged in clicks, display that page."