KeyDrop describes a promo code as an alternative to a referral link. When a user activates a partner code and makes a qualifying deposit, the account can be associated with that partner under the current affiliate rules.
The referral system is dynamic: KeyDrop states that a user can be linked to the partner whose referral link or promo code was used most recently. Affiliate payouts, withdrawal thresholds and partner rates can change, so current terms should always be checked in the live affiliate panel.