Just Use It
Qualys is a quite old name (end of last century), and in my memory reputable and well connected including IBM. Doesn't mean it's safe to use their checker but it's not the same as adding an add-on from an unknown scammer.
My advice - run the tool. If you don't have enough experience to trust it, you don't have enough experience or knowledge NOT to use it :-) But if you can protect yourself normally, it's a useful extra tool and I thank theregister for linking to it.