I notice that many Radio UserLand weblogs include a coffee mug icon. This icon allows Radio users to subscribe to a weblog with a click or two, instead of fooling around with RSS feeds manually. It's a good idea, and I'd like to add this feature to my site. One problem: I've dug around quite a bit, and I can't find any documentation.

Can non-Radio weblogs participate in this system? And if so, how? I'm perfectly willing to spend $40/year on Radio, if that's what's required, but I'd like to keep using my own tools.