Advice about extending previous development (etiquette and protocol)

I am working to extend the already excellent Symphonic Orchestra Soundfont, which is a free and open download, as a part of the process of learning Polyphone. I have already beefed up the horns section with some crossfading techniques. I am searching for some "how to be a good neighbor" information; I don't yet know everything I should know about interacting in the free-and-open-source world, such as when and how to properly extend credit or contact the previous developers.