I remember swimming in the natural pools carved by the falling water in my youth. Before the opening time of the waterfall, there were alarm sirens to tell the people enjoying the bath to get the hell out of there. Good times. Nowadays it is strictly prohibited to even get close...
Nowadays it is still accessible? The article states: ‘ The falls usually flow from 12:00 to 13:00 and again from 16:00 to 17:00 daily, with extended hours on holidays. There is an entrance fee to access the falls and its nearby areas. Visitors can follow a path leading to the falls' summit. En route, a tunnel provides access to an observatory adjacent to the falls. Another observatory near the peak offers a panoramic view of both the falls and the Nera Valley below’
Yes, the article is correct, but it misses some nuances. After paying the hefty fee (it has always been free, and it still is if you are resident, at least up to 5 years ago it was) you can walk along a path that gets near the fall, but not inside it. If you pay even more to get a "guide" you can reach an observation point (the tunnel) where you can almost touch the water, and get a free shower in the process. All in the name of "safety" (aka: money) even if as far as I know only one suicide has been registered, in the 80's.
The pools are of course dangerous, but the place that can be visited is the wall (panoramic spots and, IIRC, the back of the waterfall).
Wikipedia has a map [0] which shows the extent of the ancient lake (Lago Valino) the Romans drained (the waterfall is in the upper left corner). This lake had a surface area of around 90 km², which is roughly half the size of present-day Lago Maggiore.