So it seems to be a translation issue indeed.
Actually it's a bit more complicated, if my bad German and Google translate are up to it.
The issue cited in Münz's letter is not the "remuneration" (Vergütung), but that the flight falls within (or might be viewed to fall within) the definition of a "commercial operation" (gewerblichen Betrieb) or even "commercial air transport". The operations that he describes are more than just cost sharing, but include what have been termed "introductory flights", where a club charges passengers for rides. (Sie bieten regelmäßig Flüge für Gäste an, um für ihren Verein zu werben und die Vereinskosten durch das Entgelt zu kompensieren.) But in principle, under existing EU law, the broad definition of "commercial operation" might be interpreted as catching both introductory flights and cost sharing with passengers.
I understand the issue is being looked at by the Commission with a view to accommodating some sensible things, so I wouldn't expect a formal reply to the letter in a hurry.