From the Pacific Institute:
The Pacific Institute is pleased to welcome Dr. Peter Gleick back to his position as president of the Institute. An independent review conducted by outside counsel on behalf of the Institute has supported what Dr. Gleick has stated publicly regarding his interaction with the Heartland Institute. This independent investigation has further confirmed and the Pacific Institute is satisfied that none of its staff knew of or was involved in any way.
Dr. Gleick has apologized publicly for his actions, which are not condoned by the Pacific Institute and run counter to the Institute’s policies and standard of ethics over its 25-year history. The Board of Directors accepts Dr. Gleick’s apology for his lapse in judgment. We look forward to his continuing in the Pacific Institute’s ongoing and vital mission to advance environmental protection, economic development, and social equity.
“I am glad to be back and thank everyone for continuing their important work at the Pacific Institute during my absence,” said Dr. Gleick in a statement. “I am returning with a renewed focus and dedication to the science and research that remain at the core of the Pacific Institute’s mission.”
It appears that all details about the alleged inquiry, including who conducted it, are to be withheld. I think they had to clear him so as not to give any "fodder to the sceptics".