I'm a contributor to a large open source project. I have made heavy changes to a submodule of that project to support more functionality, but at this point further improvements will be outside the scope of the original project. As such, I have pulled only the relevant files to the submodule into their own repo, and am proceeding with a major rewrite to allow for these new features. The file structure is such that this submodule can live on it's own, with the original as a dependency.
My question is, what are the licensing/etiquette issues I need to follow? At this point, the codebase only has traces of the original files left, but they did help get things started. With a BSD license on the original project, what do I need to do for my forked project to comply?