Does an upgrade from V6 to V7 use the same license?

I upgraded from commercial V6 to V7. I have V6 installed on one computer and V7 on another. When I switch from one to the other it goes out and grabs my license, toggling the license between machines. Why? Shouldn’t I have a license for each?

Because you only have one license, not two. When you upgrade, it doesn’t give you a second license - only the possibility to use either V6 or V7 on one machine at a time. If you need two licenses, you would need to have bought a new V7 full license, not an upgrade.