Is it reasonable for a t-shirt to have to include a metadata text-block? Is a DVD substantially different from a print product?
I don't see a problem with listing authors in fairly small print on the back of a t-shirt, seems perfectly reasonable to me.
Can someone remind me why this matters in the first place? Is there some real world practical use that I'm missing?
Attribution by reference to a URL only seems reasonable for online reuse to me.
Seems like a really simple and easy to apply rule to me. If you're distributing online, you can use a URL. If you're not, you can't. That's what at least some people thought they were agreeing to when they submitted their content, and it's absolutely wrong to not recognize their right to have that followed.