Thanks, TC...will still post them at a couple of other sites.
If Jim is being threatened with lawsuits then you must comply with Jim's request to provide written permission from the artist.
Basically what you are doing in posting all the cartoons in one place, is robbing those other sites of the internet traffic the cartoons generate.
That affects what those sites charge to advertise.
Jim is not being mean and hard on you, it's the nature of internet business.