As the game was not released or sold in this form, and it has been now thirteen years from this build, it falls under the heading of abandonware. Wikipedia has a fairly comprehensive page on this.
http://en.wikipedia.org/wiki/Abandonwar ... _copyrightFor those interested in the short version, here it is:
Although the game was unreleased as DKP, it still falls under copyright protection. However, it has been noted that abandonware IP owners very rarely have any inclination to prosecute or pursue any form of legal ramification against those distributing builds of their property. It's not profitable, and usually if they have a problem, they'll send a C&D letter.
The big thing to note is that, as the game was not released as DKP, even if Rare and Nintendo wanted to raise a stink about it, they cannot claim any loss of profits or revenue, as they failed to make this available commercially...notwithstanding the fact that more than a decade has passed between a reasonable potential commercial release date and a potential release of this Alpha build. Also, both Rare and Nintendo are fairly well-known for being pretty lenient on people who muck about with their old stuff - in fact, Nintendo even PROFITS from this...or have you not heard of the impending MarioMaker release? Nostalgia is a huge part of Nintendo's bottom line, thanks to Virtual Console.
I don't foresee anything worse than a rather unlikely C&D ketter,