And from the same link:
"In November 2001, U.S. forces recovered a videotape from a destroyed house in Jalalabad, Afghanistan which showed Osama bin Laden talking to Khaled al-Harbi. [7] In the tape, bin Laden admits to planning the attacks. The factuality of the tape is questioned in the Muslim world: "But the BBC's Middle East correspondent, Frank Gardner, says that at street level in the Arab world, many believe the tape is a fake, a PR gimmick dreamed up by the US administration." [8]. The tape was broadcast on various news networks in December 2001."
I saw this broadcast and believe it to be credible. Also from the same link:
Shortly before the US presidential election in 2004 in a taped statement, bin Laden publicly acknowledged al-Qaida's involvement in the attacks on the U.S, and admitted his direct link to the attacks. He said that the attacks were carried out because "we are a free people who do not accept injustice, and we want to regain the freedom of our nation."