Here's a complete answer
www.jamesmaduk.com/library/mssr.pdf
but the short answer is that I have amember/with the CB plugin with Joomla and CB -
I have the amember/cb plugin associated with a "Free" product in amember, so anytime someone creates a free cb profile they are activating a subscription in amember.
I don't charge for the cb/joomla access. What I do charge for is access to the 1000 small business marketing videos that are in the joomla site. I'm protecting the license files for the videos with amember, not the joomla registration.
My joomla registration is just my way of capturing email addresses and building my list.
Hope that helps.
James.