I think it depends on what you are referring to. A kosher hamburger? Probably not. A prepackaged Kosher snack, most likely at most of the gift shops you'll find something certified Kosher.
For all but prepackaged snacks, Disney's idea of Kosher is a preplated meal which is microwaved. They do not keep Kosher kitchens. Kosher food is brought in from the outside and must be reserved in advance.
There are a few really good Kosher places in the Orlando area, maybe someone can provide the names and locations.
Anne