According to
http://www.nederlandseluchtvaart.nl/forums/f2-algemeen-general/vanaf-donderdag-site-tijdelijk-gesloten-21008/
the forum is to be closed temporarily from this Thursday (i.e. tomorrow) onwards.

For those who can understand Dutch and are interested,
http://www.nederlandseluchtvaart.nl/forums/f2-algemeen-general/over-sluiting-nlv-20974/index2.html and onwards has some more background information.