The remote development extensions don't appear to be open-source. The marketplace page for the "Remote - SSH" extension will point you to a license that says, among other things, "You may not: work around any technical limitations in the software;". The same page brings you to a github repo for the extension that contains no source code; it claims to be for gathering feedback only. I don't know how you can imply everything about this is open source, maybe I'm not looking in the right place?