The "volunteers" cannot pay self-employment tax, they don't meet the IRS requirements for self-employed people.
I seem tp remember a case a few years ago where a Bethelite filed a claim for some kind of benefits and won, WT had to pay. Maybe there's a thread about it in the archives. I don't mean the one about the auto accident, this was for health benefits or similar, maybe even for unemployment, if anyone cares to look it up.