This discussion might benefit from some of the debates about meaning that linguists, literary scholars, and (yes) folklorists have long engaged in.

To wit: to say that a song is only political if the writer intended it to be so is what in lit-crit is called "the intentional fallacy." The problem with the intentional fallacy is twofold--one, we cannot usually know what the writer intended. This is particularly true of folksong, when we don't even know who the writer is. Two, some of the most important impacts works of art have had in the world have been through interpretations the writers didn't intend. Therefore, it is almost universally accepted among today's scholarly community that a statement or work of art can have important meanings that were not intended by the speaker. Those meanings might be political, in which case the artwork would "be" political, if the verb "to be" can be used in this way.

The impact of this on the question is: all art is political, or can be read for political meaning. This is because part of the meaning comes from the hearer or interpreter, and that part of meaning is different for every hearer. I may think "This land is your land" is anti-capitalist in declaring that the land belongs to everyone, not just landowners. This was probably part of Woody's intention (especially taking into account the "private property" verse that he rarely recorded). But many think it merely rejoices in the natural beauty of the United States. Because of this, it is taught, quite uncontroversially, in many government-funded public schools where other communist songs would not be tolerated. Similarly, Amazing Grace has lyrics that are not political, but nevertheless it carries political meanings for many hearers.

Songs which may not have been intended politically nevertheless tell us a lot about the politics of the time and place when they were written. They document political realities of their times, can be read for political meanings, and in that sense are political.

Diane's statement that "songs intended to make money are not political" is itself a political judgment. It starts by drawing a distinction that rarely exists--most songwriters write songs hoping to express themselves AND ALSO to make money, though most are more successful in one direction than the other. It then uses that false distinction to suggest that capitalism on the one hand, and honest self-expression on the other, are antagonistic, which is a politically-charged, anti-capitalist idea. A believer in capitalism would say, "What is true self-expression but emotional communication with other people? And what better proves that a song is communicating its message than good sales? Writing to make money and writing to express yourself are therefore the same thing." I don't really buy either side of this argument, but I do think the introduction of the profit motive muddies the waters--whether a song is political is independent of whether it is intended to make money.