> If it’s the former, a vacation seems like a totally legitimate use

Imo hiding that the funds were used even in a legitimate case makes it improper. If it was intended to be paid as a salary then they should have disclosed that $x were paid out as a salary. As I understand it, the only reason we know that the funds left the project was because one of the founders revealed the use of funds by the other founders, not through a planned, transparent, or regular process. In other words, the revelation that funds were being used seemed to be an anomaly as opposed to a regular practice.

The original open letter states essentially as much: "It's fine for developers to be reimbursed for their hard work, but it should be done in a fair, transparent and accountable way."