As far as I remember Gary Larson has asked that his work isn't shared by 'fans' on the internet. It was a few years ago so i'll have to dig it up.

The company mentioned in the OPs post are a large international business that will protect their clients IP and have done so on many occasions.

In this instance I think it would be an easy IP case for his lawyers to win as Mr Larson has made clear his feelings on the use of his work on the internet.

edit: found the link to his request. http://web.archive.org/web/20130807052556/http://www.creators.com:80/a-note-from-gary-larson.html