Copssh version 6.0.0 is a major update and uses now LibreSSL instead of OpenSSL as the cryptographic library provider. 

LibreSSL is a version of the TLS/crypto stack forked from OpenSSL in 2014, with goals of modernizing the codebase, improving security, and applying best practice development processes. Primary development occurs inside the OpenBSD source tree with the usual care the project is known for. On a regular basis the code is re-packaged for portable use by other operating systems (Linux, FreeBSD, Windows, etc).

See https://en.wikipedia.org/wiki/LibreSSL for more detailed information.

We have also upgraded Cygwin and GNU tools to their latest available versions.