Any SSH server developed for ReactOS would need to be written in C/C++ and be compilable by both GCC and VC++. So while the expectation is that a developer would likely need to pull a SSH library from an existing source such as OpenSSH, the server itself will almost certainly need to be written from scratch if only because there does not exist as far as I am aware of a fully open source SSH server that runs natively on Windows without hauling around the likes of cygwin. Apache Mina is written in Java and therefore would be inappropriate as a starting base for the SSH server project.