Software licenses are the greatest legal psych out of my lifetime. US law permits anyone who has a legally acquired copy of a piece of software to copy it further[1], such

  that such a new copy or adaptation is created as an essential step in the utilization of the computer program in conjunction with a machine and that it is used in no other manner

As anyone can see, this completely obviates any need to be licensed to use software once the seller has lawfully sold you a copy. It's yours and you can execute it as you see fit. Interestingly, this doesn't really affect the GPL because the GPL doesn't attempt to kick in unless you further redistribute. And that, of course, is not protected by section 117 and does require a license.

Of course we live in a regime where the process is the punishment, so if you're high profile you'll probably get hit with a ruinous lawsuit anyhow. C'est la vie.

[1] https://www.law.cornell.edu/uscode/text/17/117