Danny Wool, a former member of the Wikipedia team, has come forward with allegations of misuse of expenses by Wales.
"Jimbeau [Jimmy Wales] was certainly not frugal in his spending on his endless trips abroad, but when it came to handing in receipts he could be somewhat careless," Wool wrote on his blog.
"At one point he owed the Foundation some $30,000 in receipts, and this while we were preparing for the audit. Not a bad sum, considering that many of those trips had fat honoraria, which Jimbeau kept for himself."
Wales has denied any wrongdoing, insisting that he claimed less than he spent. He has been supported by other members of the Wikipedia board.
Foundation executive director Sue Gardner described the allegations as unfounded. "Jimmy has never been reimbursed by the Foundation for personal expenses, nor has he ever asked to be," she said.
"The expenses he incurs on behalf of Wikipedia are modest and in no way
"Jimmy has consistently put the Foundation's interests ahead of his own, and has erred on the side of paying for his own Wikipedia-related expenditures rather than the reverse."
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