Can you give explanation what is that "merit sources"? Is it a particular section of the forum where users that will post there will automatically recieve merits or is it a group of users that have extra Merit to give users?
Merit sources are special users that gain additional sMerit (source merit) every month.
You can think of those like a bonus balance, a merit source can reward a lot of Merit without having the need to gain any Merit themselves.
This all is mentioned and discussed in the announcement thread. You can read about it there.