Since the download can be made from either the freeware or the official Grisoft site, I would imagine the chances of getting a "nasty" with the program to be virtually nil. (Except for the program itself, of course.
)
'Tis just the license key that goes with it that you get for free.
Grisoft must be getting a bit desperate to peddle their suite, perhaps.
SiteAdvisor (McAfee) is notorious for FUD. Use at as a bit of a guide, not gospel.