Photoshop brush credit

I know people use photoshop brushes in their designs, but how do you credit the brush author properly? Especially when done in commercial work? Do you provide a link or a blog posting on your website telling people that you used a brush on your latest commercial site or work?

I know I can also purchase the brush, then not have to worry about crediting. I just find those terms odd when its like, “You may use this brush on a site with less the 500 hits a month.” Or having to renew it every year.

It also makes we wonder when you see WordPress themes being used on commercial sites, does the original designer of the theme just credit the brush creator?

Thanks!