CubeSQL can can be freely downloaded from: https://sqlabs.com
If you fix any issue or improve the extension please share your changes.
The official reference should always be the C SDK. When linked in another project the CUBESQL_DISABLE_SSL_ENCRYPTION macro can be used to skip the usage of TLS code (LibreSSL). Starting from version 6.0.0 LibreSSL is the default static TLS library (OpenSSL is no longer required).
Marco Bambini (marco@sqlabs.com)