Hmm well the place i had originally read it is gone now and this is the official WOW page
http://www.worldofwarcraft.com/policy/ui.html about it and your correct they do not imply that there.
Anyhow like i said im not here to debate what bliz said or didn't say or how exactly it implies. Either way i dont agree with bliz. You should be able to charge for your addons, hide your code from the public, and for that mater what ever else you would like to do with your own code. But once again im not here to argue this. A few people here already know how i feel about blizzards policy's on addons.
Simply put i would ask for permission if your going to change other peoples addons code and redistribute it.
If your simply redistributing i personally dont see it as a problem and was advised by WOWI that giving do mention would be adequate.