what's the rule about referring other posters to sportsbooks?

[Louisvillekid1]

Just asking, because Trying to post up @ Heritage, and when I try to open a new account the fine print says

"We make our sign up page available to invited members. If you have received a current Heritage offer or promotion, please complete the sign up page to begin your Heritage experience. If you do not appear on our invited guest list a new account will not be generated."

Thanks in advance...