It could be custom coded ...
Try this guy -- I spoke with him he is OK with Adult
IDK about the multilevel aspect you would have to read the docs.
He packages this affiliate management program SaaS
Affiliate Fraud Prevention - Fraud Prevention Tools – HasOffers Support
hasoffers-affiliate-CPA-management-tools
HasOffers Pricing & Editions - Performance Advertising Software
http://developers.hasoffers.com/