I'm in a similar boat.. I'm trying to recreate Squad Leader by Avalon Hill in a browser. I think Hasbro might own the trademark, but I don't think copyright applies to game rules:
The ideas in the rules cannot be copyrighted, but the specific text of the rules can be (see http://www.copyright.gov/fls/fl108.html). Also, game mechanics can be patented.
Another way to "short" is to buy put options. The most you can lose is the price of the option. Are there any puts for Linked In? I'd buy those... maybe.
HTML5 is part of the way there but many browsers still crap out over trivial stuff. For example, for a long time (still might be true), Chrome would go nuts if someone tried to play an audio link that produced a 404 error.
So, this isn't a comprehensive answer, but hopefully shines some light on where HTML5 actually is with regard to providing an experience similar to a native app.
fkd