If you're going to base an "application-level communication system" on it, why not just use SSL instead of SSH? If you don't need the "actual sshd features" (assuming you mean user authentication and command execution), I would guess that SSL is a better fit. To have an SSHD under Win32, you have to hack a unix-y authentication somehow, which seems like it could be a frustrating can of worms to open, especially if all you need is an encrypted channel for communication.