macca - comchoice are one of the principal members of the dvd-extra alliance, and snapTV are one of comchoice's clients (via comchoice's Studio Cognito). Comchoice are (and have been for a while) actively using DVD-Extra for interactive dvd production. Whilst it is possible that Comchoice may buy dvd-extra and spend weeks/months training to use it, and then not actually use it for their client's dvd games, i just think the probabilities are greater that SnapTV Interactive DVD Games use dvd extra. But then i could also be wrong ...
By the way, the interactive dvd store is now open for business. Well they did say "opening December 2004" didn't they?