Homie Bear raises his eyebrows

Is it true that Coca-Cola owns the trademark on santa's image but allows it to be used as if it were in the public domain?

he writes

and quite reasonably too since The Green Man has been known to drift off into complete fiction when the fancy takes him. In this case however the assertion was completely kosher. Up until 1931 Father Christmas was dressed in green. On the right you can see the image from the original 1931 Coca-Cola advert that started the rot. It was drawn by Haddon Sunblom who was commissioned by Coke to produce a advert extolling the virtues of coca-cola in the winter months. It was his idea to dress Santa in the red and white livery of the coca-cola brand.

A problem for dominant brands such as Coke is that, if they are too successful, their brands names can be deemed by the courts to have moved into common usage and hence lose their copyright protection. Coke began to suffer this very problem and, through a concerted campaign, succeeded in introducing the term "cola" as the generic description thus protecting "Coca-cola" and "Coke"

See some of the original images here.