More information can by found on iChun's Blog.
iChun: The addon is really good, the first official mod addon I´ve ever seen. But I think you should include those stands in the original Hats mod because of many reasons:
-Hats mod does not add items, and it should be okay if it added this item
-Hat servers will not have Hat Stands because most users just have the original Hats mod and would not install this addon just to enter to a server
-Would make things easier!
Hats mod doesn't add items like you said, and therefore can run on servers without the Hats mod.
Hat Stands obviously adds a Hat Stand, and therefore has to be an addon if I want to keep being able to run Hats on servers without them.