And in fact Borland used to do exactly that. Their
license explicitly
stated that the software was like a book, and that they were happy as long
the software was only run on one machine at any given time (just like a
book generally can only be read by one person at a time). Wish I had a
copy of the license to type in; as commercial software licenses go it was
one of the best.
At one time the evil empire use to issue a license card with Windows, which
allowed you to install Windows on as many machines as you wanted as long
as the user had the card in their possession while using the machine.
Personally, I though Borland's method was much better than MS's.
Eric