According to a Dutch dahlia site, Rebecca's World is a purple semi cactus dahlia originated by Bal, A.G (Netherlands), 2001. It won an award in 2006. Looks nice to me.

Dahlia "Uwakigokoro" in this link resembles the dahlia in your link.

Here is a link that might be useful: Dahlia

I didn't buy it last year, but I'm thinking about ordering it this year. Has anyone grown it? I've seen it in a few catalogs.