The latest subsonic-standalone package has a single configuration option for port. The port is used for HTTP when SSL is disabled, and HTTPS when SSL is enabled. When SSL is enabled, the HTTP port is set to 0.
It makes complete logical sense to disable HTTP when HTTPS is enabled. Unfortunately, Subsonic currently has a bug that prevents Subsonic Premium subdomains from functioning when -Dsubsonic.port is set to 0 and inaccessible externally .
To work around this bug (at least until upstream fixes it) and to support dual http/https configurations for those that want it, I believe it should be possible to configure both ports independently. The older version of this package exposed subsonic_http_port and subsonic_https_port, but I believe the current configuration behavior is cleaner/safer for most users.
My suggestion: expose a subsonic_https_port option. If that option is explicitly present, use subsonic_port for HTTP and subsonic_https_port for HTTPS. Otherwise, use the current behavior that disables HTTP.