According to the Open Source Initiative an open source license must among all other things be "9. License Must Not Restrict Other Software: The license must not place restrictions on other software that is distributed along with the licensed software. For example, the license must not insist that all other programs distributed on the same medium must be open-source software." now GPL v2 (and all oher versions) instead require "You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License. ", basically this is the reason why GPL is considered a viral license: because any works derived from a copyleft work must themselves be copyleft when distributed (and thus they exhibit a viral phenomenon).
Now the problem is in wikipedia http://en.wikipedia.org/wiki/Compari...tware_licences
I see that GPL is approved by OSI as open source, but the point 9 of OSI and the virality of GPL should be incompatible with each other!