Yavor informed me that there is a new article on GNU's philosophy page.
The author Bob Chassell writes about why he think it is bad to talk about viral if you talk about strong protecting licenses such as GNU GPL. He suggests to call it vaccinates. I am also using this expression when explaining strong protecting licenses, I think it helps people understanding it better (I first heard it in a speech from Georg iin 2004).
So here is the link to: "Viral Code and Vaccination" by Bob Chassell.