It can't - it depends on your honesty not to use the same license on different computers that are "electrically" separated.

I was wondering how long it'll take until someone asks this question. What you refer to is usually called "virtual dongle" or (to use a more professional term) "activation key".
It was once supposed to be introduced with the first ProPack bugfix release, which caused a firestorm and eventually was withdrawn a couple of weeks later.

Because of that experience I would assume that it won't come back "through the backdoor" again, so if the manual doesn't state clearly that you need an activation key, it is probably safe to say that it doesn't.
However, an assumption is an assumption is an assumption (Gertrude Stein :-)

Even the suggested PPP protection would have allowed to install on 3 computers, so if anybody know for sure about P5, I'd appreciate to get the information.