The head of the Wikimedia Foundation, the nonprofit that runs Wikipedia and related websites, has unexpectedly resigned. Lila Tretikov said Thursday in a statement that "with great respect," she has tendered her resignation as executive director of the Wikimedia Foundation. "The Board tasked me with making changes to serve the next generation and ensure our impact in the future," Tretikov wrote. "Driving these changes has been challenging, and I have always appreciated the open and honest discourse we have had along the way."

Tretikov's resignation comes at a time of unprecedented tension between the community of editors and the Board of Trustees that runs the Wikimedia Foundation. Last month, a newly appointed board member stepped down after hundreds of editors signed a "vote of no confidence."

Following that resignation, a second uproar arose over a $250,000 grant from the Knight Foundation to help Wikimedia Foundation create a "knowledge engine" that would improve search. Some activist Wikipedia editors had been asking to see documentation about the Knight Foundation grant for several months, but Wikimedia was not forthcoming with the details.

Earlier this month, documents related to the grant were leaked to and published by The Signpost, Wikipedia's online newspaper. In a special report, The Signpost published the 13-page grant agreement and ran an article asserting that the "Knowledge Engine" would be, contrary to statements by Jimmy Wales and other board members, some type of generalized Internet search engine. "The presentation contrasts the ideals and motivations of commercial search engines—they 'highlight paid results, track users' internet habits, sell information to marketing firms'—with those of 'Wikipedia Search', which will be private, transparent, and globally representative," wrote The Signpost. "It repeatedly stressed that "no other search engines carry these ideals."

Those revelations caused more consternation amongst editors. Some worried that the Foundation was trying to "compete with Google," working on a general-purpose search engine that should be seen as "out of scope" for a nonprofit dedicated to providing free knowledge. Other editors saw the project as a conflict of interest for Wikipedia founder Jimmy Wales, whose for-profit company Wikia could benefit from having Wikipedia spend large amounts of research money on search. Wikia tried to create an open source search engine but abandoned it in 2009.

The following week, William Beutler, who writes a blog called The Wikipedian, wrote an essay entitled "Search and Destroy," describing an acrimonious relationship between Tretikov and a Foundation in "open revolt."

"In recent weeks, WMF staff departures have accelerated," Beutler wrote. "Within just the past 48 hours, employees have begun speaking openly on the web about their lack of confidence in the leadership of executive director Lila Tretikov."

"Lila, Jimmy, and the rest chose to keep the project and the Knight Foundation application and grant a secret until the projects were underway for six months, and even then this only came to light because it was leaked," Ashley Van Haeften, a UK-based Wikipedia editor who initiated last month's "no confidence" vote, told Ars in an e-mail exchange. "The secrecy is what stinks for the Wikipedia community, as we all know that if this was discussed in public it would have been shot down in the beginning. However, they are exciting 'Silicon Valley' style projects which non-Wikimedian board members (who tend to be Silicon Valley 'names'), and most of the Executive staff, would like on their CVs."

While the conflict over a search engine may be too "inside baseball" for many casual users of Wikipedia to follow, there is clear tumult in leadership at one of the world's most popular websites.

Wales came to San Francisco over the weekend to meet with staff, he said in a message posted to the Wikimedia-l public mailing list. "By now you of course have heard that Lila is leaving us, and my hope is that we're going to enter a new era of stability and productivity," Wales wrote. "And for that to happen, the board—including me—needs to hear from you, to listen and learn."