Oh, oops, you're thinking about position. I thought you were concerned about the opened-out navigation bar taking up too much real estate. So I was thinking only of disabling the popup element.
I don't have the exact UA-detection formula at my fingertips, but it's quite basic; you can find it anywhere, down to and including w3schools.
It's not really a matter of "disabling" a script. You'd be adding one nest to the structure:
if (action is mouse-hover)
if (user-agent is on this short list-- or is NOT on this other short list, whichever is convenient and appropriate)
carry on with the function.
Menu activation is something that typically happens more than once on a page, let alone more than once on a site, so you probably don't want to check the UA every time. Check once and set either a global variable or a cookie, depending on how long you want it to last.
:: detour here to do what I should have done in the first place: check the actual link with an iPad ::
There's a preliminary hiccup where the navigation footer expands and drifts upward as I scroll, but as soon as I "click" it collapses and stays at the bottom. There may be a glitch in the way your source site detects user-agents. But, hey, nothing wrong with writing code that's better than the original ;)