I'm not getting that message, Alan, because I'm already a premium member, so I can't answer your question specifically. They started asking for donations a couple of years ago and then encouraged people to pay $24 a year for a premium membership about a year and a half ago because they're really hurting for money. All of the work on the site is done by volunteers, but there are other costs, and there's never been a single ad on the site, so there's no advertising revenue.
As far as I know, regular membership is still free, and there are a few perks with premium membership, but the only one I remember is access to detailed lineage info. I just think it's a site well worth supporting even if the donation or membership fee doesn't offer extra perks. I use the site literally every day and I would be crushed if it were to disappear for lack of income.