This is the "Borland license", because it was first used widely on Borland's compilers, and it's probably one of the more highly-respected non-open-source licensing schemes amongst geeky types because of its simplicity: "use this software like a book".
It is generally far more sensible than the "you can only install this on one
machine"-type license. After all, what you pay for is the *use* of the program,
not the actual pattern of bits on the hard drive. Single machine licenses are
sort of like a book publisher saying once you've bought a book, you can't read
it anywhere but in your home.
This way you can buy software and use it both at home and at work, or on your and your spouse's computer, without having to buy two copies to stay legal. It also means that a company of 50 where everyone needs to be able to run some software which is only run rarely will only need 2-4 licenses, not 50.