Q:

Would a scope from an air gun work on a "real" gun?

I am an avid air gun shooter, and have been for many years. I recently got rid of most of my air guns, replacing all but one with the Umarex Hämmerli CR 20s. The CR 20s comes with a Walther 3-9x40 scope.
Living in Norway, there are some significant restrictions on firearm ownership, but one of the ways to get around that, is to be a licensed hunter. I will take the requisite course and exam this coming spring, and will be acquiring a rifle after that.
The rifle I am currently looking at is the Tikka T3 Lite .308 (Links version, though I don't suppose that should make any real difference).
I assume it would likely be a bad idea for me to use the scope off the Hämmerli on the Tikka (though I don't know that it would). What I am wondering is why (or if not, why not).

A:

Adjustable power scopes are inherently less sturdy than fixed power scopes because they have more moving parts. A .308 has a fair amount of recoil and after repeatedly firing it could shake loose parts in a scope not designed for that purpose. It all depends on the scope, but an airgun scope would likely fail after a while if mounted on a .308.

A:

The issue isn't really variable vs. fixed power - it's whether the scope in question ("Weaver 3-9x40" is probably at least a dozen different scopes) is suitable for a high-power rifle or not.  
Most rimfire (and probably air-rifle) scopes are going to have a 30mm or smaller objective; I'd venture to guess that with a 40mm objective, it will be fine on a .308 .   A quick email to Weaver support (with your scope model) likely will get you a real answer (as well as advice on what mounts you'll need.)  
Happy shooting!

