I just learned about copyleft, and Artlibre, and my innate socialist tendencies embrace the concept (as well as the clever name and the nifty symbol). Too much of the internet is used for monetary gain, and the concept of sharing material (musical and otherwise) just for the sake of creating community seems to have faded.
There are people who assume that if sheet music is offered online for free, it must not be worth much. I have a very different concept of value, particularly when it comes to my creative work. I believe that the more something is used, the more value it has.
Baby clothes gain value with each child that wears them. Children's books gain value with each reading, and they don't lose value when they are passed on to other children (unless they fall apart). Musical instruments gain value with age. Written music gains value every time it is played. I hope that the music I write and distribute for free by way of the internet (and I promise that the pieces I have in the public domain will stay there) gains value by being played by people who want to play it. Music gains particular value when it is played by excellent musicians.
I find this position empowering. The joy I get from writing music is in the writing and in the hearing. It is not in the selling (only 10% of the cover price of a commercially-published piece of music goes to a composer anyway). The time and thought that musicians put into an interpretation and/or a performance of a piece I write is ample payment for my efforts.