Is it okay to have a great horned owl to be your pet?

By strict federal law, in the U.S., you cannot keep any bird of prey (raptor). Specifically, you can't buy, sell, keep, kill, harm, or harass one. You can't even own a dead one.

It takes very special permits to be an owl caretaker.

However, if a barn owl decides to live in your barn or owl box, and you don't interfere with it, that's OK. In some areas, it is legal to own a non native species of Birds of Prey, which includes owls, but I wouldn't take the chance unless you know for sure.