Welcome to ScamWarners. I looked and that website has been registered since 2007, which scam and fake sites don't register for more than a year and don't last very long at all.
I do not have personal experience with the site or any of the services it offers. It is important to remember that even legitimate sites can have scammers on them. I do not know the real estate rules in the Netherlands. Having said that, if the laws are similar to those in the USA, to advertise on certain sites it is necessary to gegistered and licensed as a real estate professional. This may be true with this site as it says
Welcome to Netherlands Properties a network for fully registered Brokers
The site also leads to the MLS (Multiple Listing Service) which is for real estate professionals to list their properties.
I hope this helps.
Bubbles, former Scamwarners moderator.
Rest in Peace 24 June 2015.
Gone, but never forgotten.