How to navigate at Familiekrøniken:
Go to www.familiekroeniken.dk
Select 'Søg i Familiekrøniken'
Under 'Navn', enter the first name on your list, i.e. Niels Nielsen Gundestrup, and hit Enter.
One name appears: Click on this name, and you reach the family tree you were asking about.
On the line that starts 'Stamblad', you get the name of the family tree owner, Martin KI Christensen.
Click on 'send mail' to contact him.
Hope you find what you are looking for.