I assume you have an USB logger?
WeatherDisplay:
AFAIK, the WD-program / app will not upload to WeatherLink.com in that case
WD will read the data from the USB logger and can do all kind of uploads but not to WeatherLink.com
WeatherLink.com version 2
You are using WeatherLink.com version 2.
Version 2 does not need the userid, the userid is only used for logging into your account.
An API-key is now needed to download the data from WeatherLink.com
Upload to WeatherLink.com
To upload to weatherlink.com v2 you need to use the weatherlink-program/app or an IP-logger, [although there are other third-party loggers which seems to are able to upload also].
If you only want to use the data from the Weatherlink.com website in your own website, it would be easier to use the Davis IP-logger.
You will not need your MAC to be running 24/7 with an ip-logger.
Wim