Well sure, but what if I created a sponsorship page instead? Like the one I linked to above. Would that constitute that I’m “selling links” or would it rather be a sponsorship of the site that as a bonus, received a linkback?

it’s all a gray area

See there are many ways to find out if your publicly selling links on your site.

If you don’t have a Buy Link page, google can’t find out if you are accepting paid links. You link to someone just like that for showing your gratitude. I think its fine . He becomes a business partner for you etc. But others say this can be deemed as a paid link.

I agree, Google does not pay to get the linkbacks, but then this raises a good point.

What if I had someone wanting to just pay me and I happen to link back to them? Is that considered a paid link or is it considered just me being nice?

There’s a very fine line and Google doesn’t know where it is.

they are a heavy user of apache and want to support it.

tats my 2 cents

It’s likely not passing much link love though, still might be passing some though. Even still, an authority link from Apache would definitely be nice.

You could even donate $5,000 for the bronze sponsorship and it seems they don’t add nofollow to those links.