They state it is for irrigation only. You can use the same technique for drinking water in some places, but it really depends on local soil conditions (meaning even if your neighbor has safe water you might not get safe water!) and the care taking when drilling the well. If you do try this, after drilling and sealing the well you chlorinate the water (to kill anything you introduced), wait a week, then have a proper lab test, if the lab says it is safe to drink you are fine. The lab test should be repeated every 3 months (almost nobody does, but that is what the labs tell you)

You can sometimes work around this by installing filters (RO and otherwise), and UV lights. However you need lab results to tell you what filters to install, and you need to keep those filters maintained.

The quality of the water depends on the location.

This particular method of drilling a well works in sandy soil or clay where the water table isn't very deep. If you're in mountains or on any topology with bedrock you'll need better equipment, particularly a carbide or diamond tipped bit. And you'll be drilling potentially hundreds of feet. Something like this would most certainly not work in Colorado, it would probably work in Florida or Louisiana.

I certainly wouldn't drink water out of a shallow well most places. It is worth every penny to get someone to drill a 200 foot well and not have to worry about contamination for drinking.

No, the website says this is generally non potable water.