"Free +" Apps

Some apps are "free."  Others are "free +."  Would you know the distinction? The mother of an acquaintance of my wife's says it best in her words:

"I have three kids and each one has an iTouch. They love to download game apps, and I told them that they needed to check with me before downloading it so that I could approve the price of the app (meaning I didn't want them to spend over 99 cents per app--I know, I'm cheap!).

"What I didn't realize was that some game apps are labeled "Free+". I didn't know what this meant until I looked at my Credit Card bill and  saw almost $40 worth of charges for game apps that I thought were free! The Free+ apps mean that you download them for free, but then you can purchase things while using that app, and it does not require you to put in your Apple ID password again to purchase. So my son had bought "extra powers" through a game called Lite Bike that cost $16! My youngest, who is 5 years old, had also bought things through a game app called "Tap Zoo".

"I took care of this by making them pay me back and deleting all the apps that were "Free+". They may not download anything that's Free+ and must always ask for my approval beforehand. Downloading apps, even 99 cents at a time, can come back to haunt you!"

So I wonder ... is this legal?  Undoubtedly it is.  The disclosure on the accept buttons most assuredly had this information (and most of us don't read all that mouse-sized type).

But good business practice?