Well, here's what I got from the wikipedia entry for Z:OOT:
Ports and re-releases
Ocarina of Time was re-released for the Nintendo GameCube as an emulated ROM, as a combo with The Legend of Zelda: Ocarina of Time Master Quest and as a part of The Legend of Zelda: Collector's Edition.[57] The former was released as Zelda no Densetsu: Toki no Ocarina GC in Japan, with the Master Quest side named Zelda no Densetsu: Toki no Ocarina GC Ura. The "Ura" name stems from Master Quest's origins, as an expansion to Ocarina of Time to be used with the Nintendo 64DD under the working title Ura Zelda.[59] The Master Quest compilation was given as a premium for pre-ordering The Wind Waker in Japan and North America,[60] as well as in a special GameCube bundle at Wal-Mart (the disc came in the same case as The Wind Waker in the GameCube bundle). In Europe and Australia, the disc came in the same case as the initial pressings of The Wind Waker.[61] In Europe, it was available for a limited time through a special offer on the Nintendo website. The Ocarina of Time Master Quest box contains a single disc which includes the original game, the Master Quest version, and six video demos for various games for the GameCube including one for The Wind Waker and a video demo of the GBA re-release of A Link to the Past.[57] Master Quest uses the same engine and plot of Ocarina of Time, but dungeons have been altered.[57] Collector's Edition was available in GameCube bundles in Europe, Australia and North America, as well as by registering hardware and software, or by subscribing to official magazines or clubs.[62] In addition to Ocarina of Time, the disc also contains the original The Legend of Zelda, The Adventure of Link, Majora's Mask, a demo of The Wind Waker, and a Zelda retrospective.[62] The original game is displayed on the Nintendo 64 with a resolution of 320×240, but the GameCube emulations run at 640 × 480 and support progressive scan.[57][63] The game was released in Europe and Australia for the Virtual Console on Nintendo's Wii console on February 23, 2007 for 1000 Wii Points. It was released in North America on February 26, 2007 and Japan on February 27, 2007.[64] This version is an emulation of the Nintendo 64 version, but does not support controller vibration, rendering an in-game item titled the "Stone of Agony" to be useless.[25][65] The Wii can play the GameCube compilation versions with this feature intact. A five minute demo of the game is included as an unlockable in Super Smash Bros Brawl
So basically it is indeed emulation, and since the original textures were designed for 320x240 and not changed (it's a ROM after all), it's not only running in emulation, but being upscaled (very well though). The fact that the GC, far less powerful than any computer even of its time, can emulate OOT, upscale it, use progressive scan on top of that (doubling the data fill rate) and running at 30 FPS, is massively impressive to say the least when even today's strongarm computers can't run N64 games at any consistent framerate, scaled or not scaled.
The ROM nature also explains a lot about why there was virtually nil load times. Very nice. Now I want to go back and finish my game. I really need to find some GC component video cables...S-Video just does not do it justice.
