If you pay to have a doorway included in a database is opened to banning?
If they willing to accept payment I say no ban.
If the page returns the information the user is looking for, I say no spam.
Doorway pages are created to get around pages that are designed with only design in mind.
If you can create a doorway that includes many of the design properties of the original and meets the requirements of the database algo, you have a value added quality product that delivers both to the user and the client.
Is this spam?
Not in my book.
Will it be banned?
After all it is all about fair and free enterprise.