Not sure how this is going to work. I reckon abc is the way to go, but I think it's important people can get tunes directly if they don't know it, so I might look into setting up some sort of web service so submitted abc can be PDFed. Thoughts welcome.
Copyright: you can't include copyrighted material here without the owner's explicit consent. However, if you're not sure, put it up, and if a copyright holder does come knocking we can easily delete it.