The first is to dissallow someone else using a copy whilst you are using the other, or for your simultaneous use to be editing a second image whilst applying any longish procedures to another on the other PC, using it twice sumultaneously rather than buying two copies.
The second applies to volume licenses, as it says, not home users such as you and I, it could also be arguably to dissallow commercial useage for benefit of others I suppose?
HTH.