Commercially, using the tune 'Happy Birthday to You' does not cost anything anymore since a federal judge last year declared its copyright invalid. Now the same can happen to the civil rights anthem 'We Shall Overcome.'

A non-profit foundation bearing the same name as the anthem that works with orphans and the poor sued the music publishers who control 'We Shall Overcome' asking the judge to declare that the song is not under copyright and is in the public domain, reports The New York Times.

The case was filed at the Federal District Court in Manhattan where it seeks class action status and return of unspecified amount of licensing fees the publishers, the Richmond Organization and Ludlow Music, have collected from the use of the song.

The suit alleges that 'We Shall Overcome' was an adaptation of the spiritual 'We Will Overcome' which was first mentioned in print in 1909 in The United Mine Workers Journal. By the middle of the century, it was firmly established as a protest hymn and as anthem of civil rights movement. The suit claims that the copyright of the song was not as broad as its publishers assert and has long since expired. 

Ludlow, the publisher, filed a copyright registration for 'We Shall Overcome' in 1960 but the lawsuit said the registration covers only the arrangement of the song and some verses, The Seattle Times reported. The lawsuit cites a study by a musicologist who said that this version of the song is essentially the same as one published in 1948, whose copyright - if ever it was valid - would have expired in 1976.

The case started as an attempt to license the song for a film. The We Shall Overcome Foundation contacted the publishers several times to seek permission to use 'We Shall Overcome' for a documentary about the song but they were rejected.

That's when they approached the firm Wolf Haldenstein Adler Freeman & Herz who, Reuters reports, are the same lawyers that last year won a ruling declaring the world's most popular song 'Happy Birthday to You' not subject to copyright and is in the public domain.

In February, Warner/Chappell Music, a unit of Warner Music Group, agreed to pay $14 million to end the 'Happy Birthday' lawsuit and drop its copyright claim to the song.