Using code base of OpenVPN (GNU GPLv2 license) in proprietary closed source project is under consideration. OpenVPN uses OpenSSL (Apache License 2.0). Changes in OpenSSL are needed only (OpenVPN will be intact). So OpenSSL has permissive license (allows changing of license of proprietary project) and OpenVPN - strong copyleft - license can not be changed.
If changes will be in OpenSSL only is it legal to distribute part of proprietary project as closed source (hide changes in OpenSSL)?