The rules concerning use of these locations vary slightly. All set a limit to the duration of your stay. This ranges from 24 to 72 hours. To my knowledge no-one has ever been asked to leave though, even when staying longer. Since camping in the wild is not allowed in the Netherlands, it is mandatory to stay reasonable close to the sign which designates the campsite. Again, this rule does not appear to be set in stone.
Two rules are absolutely essential. First, do not leave any garbage. These places are often in remote locations and campers are expected to pick up after themselves. Second, do not make an open fire. On some campsites you'll find a hearth, but on most you won't. An outdoor gas burner for cooking your meal or water is no problem.
Kaart", meaning map. Here you'll find a Google Map with the exact locations of all the campsites. Under "Locaties" you'll find a list of all the locations, including some which have been removed and some of which their current status is unclear. These are not shown on the map. At "Locatiebeschrijvingen" you can find more information (in Dutch) and pictures of a select number of these campsites.
Enjoy your stay in the Netherlands!