"The GPL benefits the original copyright holder..."
The post is generally true, but don't forget the end-users. It is important
to emphasise the gains of the end-users as the benefits of the copyright
holder are only a side effect of the user protection, which happens to be at
the cost of limitting the intermediate developers. If you put the end-user
out of the equation you end up missing the whole point of the Free Software
idea.
On topic: Fortunately there seems to be no case of a non-copyleft free
program loosing ground to a proprietary fork. ...yet.
