I've heard tell that some software out there will refuse to operate on Windows Server because of licensing, like perhaps they want you to get a business license. I have no evidence at hand, but something to look into.
I worked at a software vendor where we would check the type of product and yes you needed our server product to run on their server product, whether or not you used the server as a server.
Not all software does this but I also don't recall it being unusual.