IF I remember correctly the trick Art used in creating the Mach3 Driver is based on an old hackers trick to gain access to the OS and take control. A good AV may see this as a legit virus BUT it is not in this case.
There are 1000's of users that have done the download and as far as I know no one as even caught a cold much less a virus(;-).
BUT it is your choice, (;-) TP