Is making a referral/link exchange forum allowed by places like..

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I was wondering, & I have been working on a forum but I don't want to release it to the public if it's breaking any rules that I don't know of by InvisionFree forums. I was just wondering, is a referral/link exchange forum allowed by places like InvisionFree? Can anyone help to clear this up for me? I'm almost 100% sure it is, and I have the forum all set up for the most part.. but if it's not allowed, I don't want to see my forum deleted and me getting banned from invisionFree or any other free forum place I decide to use. Any info you have on this to clear up this issue would be great!