I don't know what you mean by draining it's capacity, so not sure how to answer. Maybe just explaining a bit will answer your questions though :)
chainBB performs the same actions for users on the Steem blockchain that steemit.com does. It's like the difference between using the outlook vs gmail - they both do email, just differently, yet with the same protocol. Both steemit/chainBB both share the same blockchain, so every action on one is done on the other.
As for money involved - there is a 15% reward beneficiaries split with @chainbb when posting via the site. Steemit.com is 75% to the author and 25% to the curators, while chainBB is 60% to the author, 25% to the curators, and 15% to chainBB. These funds are going to be used to help pay for expenses in building chainBB.
Hope that helps!