Only terms that I could find are within the fast track to gold:
Terms and Conditions
*For Gold status, member must be an athletic administrator, athlete, or affiliated with a sports entity, sports related company, sports group or event and must complete four qualifying stays within 90 days of registration or enrollment. Discount offer is valid on individual US travel at participating hotels and cannot be combined with any other offer. The offer (“MVP FastTrack”) is available to members worldwide who have registered at HHonors.com/MVPFastTrack and is not transferable.
So I assume what I highlighted in bold would be the general requirement. There is nothing mentioned that an athlete needs to belong to any organization, so that fits for anyone.