Viral license
See GPL and other free software licenses to understand the details of what is meant by a viral license. Usually this term implies required reintegration, which is the controversial requirement that open source objects to in both free software and Consortium license software.
Because Microsoft exploits the use of the term viral to portray both free software and consortia as being like computer virus creators, it is almost always better to refer to required reintegration directly and not use this term.