That was an overly complicated sentence, wasn’t it?
Basically “viral license” was a scare word Microsoft used in a campaign about 15-20 years ago to frighten people away from Linux and open source stuff.
The idea was to imply that the GPL was dangerous and would somehow “infect” your software, taking it away from you and making it free, so you couldn’t make money anymore.
The truth is that if you’re putting somebody else’s copyrighted code into your commercial product, without gaining their permission, you’re in trouble regardless. It’s against the law and opens you up to a lawsuit. The GPL just gives you a way to get out of it by saying “release your derivative code under this license and we won’t sue.” If you’re not okay with it, just don’t insert GPL code into your product, dummy.