Found a bit more info on this one--it seems it was on an album as well as in the movie.

Lin

From: here:

HCA045 This Land Is Your Land - Songs of Social Justice - 1964 October - UAW

This album is the one that is tied to the release of "The Inheritance" movie and contains the song for which Millard Lampell wrote the lyrics. Performers include Joan Baez (singing "We Shall Overcome"), The Baytown Singers, Leon Bibb, Tennessee Ernie Ford, Ronnie Gilbert, Fred Hellerman, Billy Holiday, Cisco Houston, Ian & Sylvia, Tommy Makem & the Clancy Brothers, Odetta, Peter Paul and Mary, Pete Seeger, The Tarriers, The Weavers, Josh White.

Judy sings:
Pass It On - (Music by George Kleinsinger, Lyrics by Millard Lampell)

Complete Track List - performer - writer:

This Land is Your Land - The Tarriers & Ronnie Gilbert - Woody Guthrie
The Ballad of Momma Rosa Parks - The Baytown Singers - Nick Vener & Buddy Mize
Four Strong Winds - Ian and Sylvia - Ian tyson
Another Man Done Gone - Leon Bibb - Southern field cry
Sixteen Tons - Tennessee Ernie Ford - Merle Travis
Johnny, I Hardly Knew Ya - Tommy Makem and the Clancy Brothers - 18th century (apparently predates "When Johnny Comes Marching Home")
Drill, Ye Tarriers, Drill - The Weavers - Thomas F. Casey
Strange Fruit - Billie Holiday - Lewis Allen
Oh Freedom - Ronnie Gilbert - Traditional
He Was A Friend Of Mine - The Baytown Singers - Buddy Mize
Blowin' In The Wind - Peter, Paul and Mary - Bob Dylan
Follow The Drinking Gourd - The Weavers - Paul Campbell
Hard Time Blues - Josh White - m: Josh White, l: William Waring Cuney
Come Away Melinda - Fred Hellerman - Fred Hellerman and Fran Minkoff
If I Had A Hammer - Odetta - Lee Hayes and Pete Seeger
Pastures of Plenty - Cisco Houston - Woody Guthrie
Little Boxes - Pete Seeger - Malvina Reynolds
We Shall Overcome - Joan Baez - Zilphia Horton, Frank Hamilton, Guy Carawan and Pete Seeger
Pass It On - Judy Collins - m: George Kleinsinger, l: Millard Lampell