If you've ever indulged in free love, voted for the Peace and Freedom Party, or shouted "Free Huey!" (clenching a fist, not a coupon), chances are you know of Mark Rudd.

He was the '60s leader of the Columbia University chapter of Students for a Democratic Society (SDS), the most powerful protest organization against the war in Vietnam. The character immortalized in Doonesbury as "Megaphone Mark," the antiwar activist.

Name still doesn't ring a bell? Well, lately, Rudd has been described as an FOB - friend of Bill's.

Not Clinton. Ayers.

Yes, that Bill Ayers, leader of the notorious Weathermen, branded by Sarah Palin as the domestic terrorist Barack Obama once palled around with, even though it wasn't true.

Well, Rudd actually did run with Ayers - and did way more than just pal around with his comrade. As one of the founders of the Weather Underground, he spent time with Ayers on the FBI's Most Wanted list, even lived on the lam with Ayers for a time in the early '70s, trying to figure out ways to blow up federal buildings.

Now, 40 years later, Rudd, unlike Ayers, is clear about what he regrets, and what he would have done differently.

And wants his own children to know his truth, which is told in his recently released memoir, Underground: My Life With SDS and the Weathermen.

He'll read from his book as part of a First Person Arts event on Wednesday at the Philadelphia Arts Bank. He knows the city well, having hidden out here in the early '70s.

The Bay Area, where I grew up, was ground zero for the antiwar and Black Power movements of the late '60s and early '70s that caused a seismic shift in consciousness throughout the nation. Too young to participate, I watched from the sidelines and retreated when organizations like the Black Panther Party - headquartered just blocks from my house - called for armed struggle.

So I couldn't help but ask Rudd why. I could understand his motive, not his actions.

He explained, via phone from his home in New Mexico, that his militancy was "a necessity to prove myself, and thinking this is the way, by being like Che Guevara and rejecting white privilege and taking risks. I did believe in it for a long time. I just felt I wasn't capable of [violence]. I felt that weakness was really an ideological rejection of the whole thing."

Middle-class origins

Refreshingly honest, Rudd writes about his road to radical: from upper middle-class Jewish upbringing in Irvington, N.J., to taking over administration buildings as chairman of SDS.

And then, getting kicked out of Columbia in 1969 after clashing with police during the Days of Rage in Chicago, and helping organize the Weathermen, renamed the Weather Underground when they were forced underground.

The group was communist in ideology, militant in deed. It didn't just ask, "Where have all the flowers gone?" it plotted to uproot the "imperialist" government.

Well, those grand plans blew up in their faces in 1970, when the crude bombs they had intended to set off at a military dance at Fort Dix blew up in a Greenwich Village townhouse, killing three Weathermen.

Running from the FBI, Rudd fled New York, spending seven years as a fugitive. He lived close to a year in Philadelphia under an assumed name.

"I remember sitting in Rittenhouse Square, reading the paper about the demonstrations taking place nationally after the Kent State killings [in 1970]. Here I was, blocks from Penn, and I couldn't even participate in the demonstration. I was completely irrelevant," Rudd recalls.

"That's when it dawned on me that I had made the wrong choice."

Since the government dropped charges against him in 1977, Rudd and his wife have lived a quiet existence. After teaching math for 32 years, he speaks at colleges and has spent the last few years tending to his 97-year-old mother, who still lives in New Jersey.

Unlike the president, Rudd really is a socialist. He still organizes - now for Latino causes - and advocates for Palestinian rights through his organization, Another Jewish Voice.

The one thing he refuses to do is talk legacy.

"I find myself arguing with young people [that] the Weather Underground was a source of negative lessons," Rudd says. "But they say, 'You give an example of a person who's willing to fight for a cause.'

"That's quite novel to some people."

Contact columnist Annette John-Hall at 215-854-4986 or ajohnhall@phillynews.com.