Revocable GPL (Groklaw)

I think your confusion may stem from an odd interpretation of the word "license".

A "license" is not a unit of permission giving a single person the right to run a piece of
software on a single machine, though in the proprietary world that may be how it is in
practice most frequently used.

A "license" is just a statement granting some permissions to do stuff with your copyrighted
work.

In this case the license promises all recipients permission to redistribute the work under the
same license terms.  That promise can't be arbitrarily revoked.