I have spent some time pondering portkeys in the last day or two and discovered there is no canon rule specifically about Hogwarts and portkeys, but that portkeys must be authorized by the ministry in general. The first quote I found specifically indicating any actual rule against portkeys was this:
"Now see here Dumbledore!" said Fudge, as Dumbledore walked over and
picked up the golden head "you haven't got authorization for that
portkey! You can't do things like that in front of the Minister of
Order of the Phoenix Chapter 36 (pg. 818 in the Scholastic edition from 2003)
It certainly showed some restrictions but I still believed those restrictions only to apply to Hogwarts until I also discovered the following quote:
"How're we getting - wherever we're going?" Harry asked. "Brooms,"
said Lupin. "Only way. You're too young to Apparate, they'll be
watching the Floo Network, and it's more than our life's worth to set
up an unauthorized Portkey."
Order of the Phoenix, The Advance Guard, Pate 52 (Scholastic:2003)
In the example above, there were a number of highly capable wizards present, Lupin, Moody, Shacklebolt, . . .
Additionally, even the portkey into Hogwart's Dd makes at the end of OoP, is against the rules because the Minister protests against it. It would seem that even though Dumbledore has the ability, he does not have the authorization to do so and even he isn't supposed to.
So, it would seem that this applies to your question in that, Dumbledore still can obviously, easily break the Ministry's rule, but in terms of legalities, no one can make a portkey into Hogwarts without prior authorization.
There are probably additional protections at Hogwarts (no canon, just assumption based on the protections against other transport to and from the castle without anyone knowing about it) over and above general ministry protections so I'd be willing to guess only those that have received authorization from the ministry is the answer to your question.
I am guessing that authorization of such a portkey onto the grounds would generally mean the ministry alerts whoever is headmaster of hogwarts at the time the portkey is authorized.
As to who created the Portkey aspect of the Tri-wizard cup? (which I'm guessing is the true root of you question), we don't really know for sure. Since, it seems, Making a portkey does not prove particularly difficult (at least for Dumbledore), I'd imagine he did it. Then, trusting "Moody" who was really Crouch, he let Moody/Crouch bother with the placing it in the maze.
The book specifies that Moody volunteers to place it in the maze (I'll find the quote, as soon as I have my book) - I think if he had also created it, the book would say that instead. Additionally, the portkey has the portus to the grandstands - something it doesn't seem to me Crouch would have bothered adding if he had been the one to create the Portkey from scratch - no reason for it (And no, I don't think Lord V wanted to return to Hogwart's with Harry's Deadbody to reveal himself - he still had to get his closest, most trusted followers out of Azkaban and rebuild his army before he would have wanted to directly confront Dumbledore).