Is it necessary, or a requireent, to buy a new license when up grading from version 3 of VMware to Verson 4
Yes, you need a new licenses for major versions, whereas updates/patches for minor versions are available for free.
André
Yes although you might want to wait until VMware Fusion 5 is released and in the mean time use the VMware Fusion Technology Preview 2012. Because the License Key expires on October 15, 2012 it is logical to assume it will go Gold on or before that day so version 5 should be available within the next two months and you can use the Tech Preview until them.