N98F was certified in the Experimental-Exhibition category. The FAA rules are very clear about carrying passengers in aircraft that are in other than Standard Category. For Experimental-Exhibition? No passengers. Let's look in the FARs!
91.319
(a) No person may operate an aircraft that has an experimental certificate -
(1) For other than the purpose for which the certificate was issued; or
(2) Carrying persons or property for compensation or hire.
Notice that it doesn't say, "No passengers," but rather no persons for compensation or hire. So maaayyyyybe...could we stretch that a little and say that people who make a (ahem) "donation" become members of the organization and thus ersatz "crewmembers" and would then be allowed? You know, a little (wink-wink) "workaround," perhaps?
Nope! Because of that first part of 91.319 - that bit about the "purpose" for which n98F's certificate was issued. For that, we go to FAR 21. We find that there are eight different sub-categories of the "Experimental" certificate.
21.191
Experimental certificates are issued for the following purposes:
(blah blah blah)
(d) Exhibition. Exhibiting the aircraft's flight capabilities, performance, or unusual characteristics at air shows, motion picture, television, and similar productions, and the maintenance of exhibition flight proficiency, including (for persons exhibiting aircraft) flying to and from such air shows and productions.
Uh-oh. We don't see an allowance for
paying-passengers-who-aren't-really-but-they-made-a-"donation"-and-so-we'll-call-them-crewmembers. Oops!
To carry passengers in a "warbird" - and it is permissible - the operator would have to have one of those
Living History Flight Experience exemptions. And Marpat did not. Double-oops!
So we don't know what's going to happen here. The FAA may do nothing, as usual, other than going after the certificates of the guys that owned and operated that UH-1B. Or they may search and come down really hard on others that are giving "warbird" rides for money...err...I mean "donations." As always, the families of those who perished in the Huey are left to pursue civil claims.