The macron on the a smacks of Heavy Metal Umlaut, but is phonetically correct: it means "pronounce long". But I'm not sure the Grāpple folks are terribly confident about it: they provide a pronunciation guide ("say Grape-L") right underneath the name.
And I rather enjoyed the hyperbole on their Making Grāpples page: "the process is complex". Oh yeah? Not terribly it's not: "Fiji apples are dipped into a combination of pure water and Concord grape flavouring".
Did I buy some? No. They cost $4 for 4; my 3 Granny Smiths cost me $1.34. And reading Steve Portigal's review, I'm glad I didn't.
But as it happens, I do have Concord grape juice in the fridge. Soaking Granny Smith slices in it does produce a vaguely grape-flavoured apple, as well as dying the apple flesh pink. I'm not sure, however, that this is altogether a good thing; on balance I'd prefer my apples to taste like apples.