Don't know if it helps, but when I was making wooden things in carpentry class in school we were told to use just ordinary vegetable oil to treat them which of course won't harm you if you ingest some. My parents still have a couple of plates I made and I think they are still holding up pretty well after almost 20 years. Of course they are not used for hot liquids, only hot pizza...
I'll ask my Argentinian friends how they treat their mate gourds and let you know...