How do they do this?
Simple. The Royal Archives don't have a true monopoly on these records as each locality retained a copy and has the right to make them available on their own.
One of the reasoning is that if more localities followed the example of the ones here, the Royal Archives would have to relinquish their grip and make the records available to all online.
BSkempen.be: Civil Registry of the Campine, Antwerp Province
As of July 1, 2011, their indexes contained entries for 226,480 records from the Civil Registry and 35,514 records from various parish registers. The number of scanned records requested was 25,385.
Access the indexes by going to their home page at http://bskempen.be/home_en.htm
Here are the available locations:
Endhout, Geel, Herentals, Herselt, Houtvenne, Hulshout, Morkhoven, Noorderwijk, Oevel, Olen, Tongerlo, Varendonk, Veerle, Vorst, Westerlo, Westmeerbeek, Zoerle Parwijs
Click on the coat of arms of the town in which you are researching and you will find a link to a zipped file containing spreadsheets of Births, Marriages and Deaths for that locality.
I don't think you will need a special program to unzip the file. It seemed to use IE to do this by itself.
If you want a look at the original record, go back to the page where you found the zipped file and click on "Scans" at the top of the page to request a copy.
There is no cost to you whatsoever.
If the file is small enough to email to you, you will find it in your mailbox. If not, they will upload it to their website with instructions on how to retrieve it. All they ask is that you let them know when you have downloaded it because they want to make sure they are not short on cyber space.
If you have time, you might consider giving some of it to help with this special project.
The site is tri-lingual so you should not have too much trouble using it.
This system is used by other groups and in fact I wanted to develop this article about 6 months ago already but got caught up in daily living.
I am waiting for the latest on this other group which offers records from the Marche-en-Famennes area and will share the additional information with you as soon as I get it.