I'm not officially stating this. But if you label it by saying
"the following link is a referral."
I think its fine.
I also think that if a link offers a link to something that has no referral you gotta post that one down to, to give the option.
So one with a referral clearly noted and one normal. If you do it nicely, I see no reason why people would choose the normal link over the referral.
