Hi Lars,
Given that I'm the one usually scrambling to keep up with WU website changes, I'm not in favor of doing a boycott of them at this time.
Their recent blocks for access were due to defensive actions against specific IP addresses that had been overactive on their webservers -- perfectly understandable action. These extra requests likely came about by having ill-behaved search engine bots try to follow all possible links on the WU-history.php page (which Jim has fixed), and not because of the light loads caused by the WU-forecast.php script.
I've updated the WU-forecast.php script to follow a 301 redirect and cache the block.asp page from their site so you can ask for the IP address to be removed from their block list. I was blocked yesterday and had the block promptly removed.
I also added in the WU-forecast.php script a User-agent: PHP,WU-forecast.php,saratoga-weather.org to the request so they can identify this WU-forecast traffic in their logs (and they'll see it's not onerous at all). John Celenza of WU made that suggestion and it was a good idea.
So, your site's IP was blocked likely for high-traffic reasons, and likely not caused by people using your site but by bad-bots following links on the WU-history page.
Best regards,
Ken