I can see how it would be possible, probably similar to the Fetlife app, an apk that is downloaded from the site and installed, independently from any app store.
I can also see it being similar to the Fetlife app, in that it'd likely just be a shittier, nerfed version of an already pretty mobile friendly site.
Does anybody need a separate app for a forum? One thing I find most helpful when using forums is the ability to have multiple tabs open, something that is almost never supported by the individual apps. Half of the apps out there are basically browsers with some skin that only shows the website anyway, utterly pointless.
As for security: you don't need a brand new app at all. If you're on Android, which I would assume you are if you're talking about so easily installing apps outside of an app store, it's simple. Use a different launcher app. I use Nova Launcher. Pretty much all of the launchers allow you to rename and change the images for app icons. Just do that. You could even clone the browser apk and have a whole separate browser exclusively for zoo stuff. Having an app just for this forum seems like a massive waste of effort.
Hell, don't most browsers let you just set up a shortcut for a bookmark on your home screen? There ya go, ZooVille app icon ready to go.