Wow, this is a super cool idea! My girlfriend actually works at a restaurant and I've worked with her on their menu design, OpenTable registration, take-out ordering system, and other things, so this subject is somewhat familiar (and of interest) to me. I love the idea of standardizing it all.
My main question is what exactly this NANY entry is. Is it the format specification, the website, an app to edit the menus and save in an open format, or all 3?
I'm also curious how are you going to encourage participation in this by restaurants? This could be a great success if there is sufficient incentive, but without that buy-in it's really going nowhere.
I see right off that it's another way to promote their restaurant, in theory (assuming the site gets popular), but I think if you offer some additional services (which you may already have planned), it could probably be a lot more attractive, e.g. allow restaurants to embed their open menu listings on their website really easily, with easy management through the open menu site, keeping their site menu and the open menu site listing in sync.
For the future a way to actually create templates that can turn into printable menus would be fantastic and probably a very desirable future. A lot of restaurants have trouble keeping their web menu, take-out/to-go menu, and print menu in sync. If you could provide a single, easy to use system for managing restaurant menus in full, with functions to embed on websites, search, and print in high quality with some decent formatting, that would be outstanding. I realize of course that a formatting system would be complex to implement, but I've worked with one that seemed fairly adequate that I think could mostly be translated to the web very easily.
Anyway the other nice thing about this of course is that the format is open, so even if you don't do all the above, someone else should be able to. Just keep your DB standard open, create an API as soon as you can, and let people run with it.
More feedback as I think of it. I'm really looking forward to seeing this evolve!